Where do we, the PCs fit into all this?
Every RPG kinda has a default assumption about who the party are and what they're all about. In D&D you're a bunch of weirdos from radically different backgrounds who all met up somehow and decided it'd be a good idea to spend your time poking into big awful mazey dungeons and/or roaming the countryside killing monsters that for some reason are all filthy rich and taking their stuff, probably with save-the-world-from-monsters intentions. In Shadowrun, you're a bunch of desperate people in a cyberpunk setting forced to do dangerous crime stuff for mysterious corporate weirdos to survive and pursue personal grudges and such. Eclipse Phase generally assumes you're a bunch of hyper-competent specialists in ecclectic fields working for a super sketchy secret society trying to quietly stop horrible sci-fi doomsday situations from happening, with an overall vibe captured wonderfully by this little slogan:
That's inherently a pretty intense and desperate vibe though. I'm totally open to something a bit more laid back, or starting with something more laid back and building to that kind of level. If people want me to run the clandestine secret agent deal, cool. If people want to do something more Shadowrunny, just trying to get by in a weird setting, that works too. Members of an anarchist gang sabotaging horrible corporations on general principle? Also a way to go. When this is more of a "we are making characters and then we are going to start playing" thing, this is something to all get on the same page about first thing. Also good to establish whether to start things off based on the Sunward side of things (where there's relatable stuff like gravity, cities, civil rights movements, infiltrating the Bass Pro Shops Arcology) or Rimward (smaller scale spaceship/station as an initial setting, nobody bats an eye at damn near anything, but harder to imagine lots of day to day stuff). Past that though...
You're one of the few lucky people to have a physical body these days, and it's probably a really good one. It might legally be property of Disney, or on loan from the public body bank, but it's not something most people have by default, and should anything horrible happen to it, you're even in a position to be hooked up with a replacement fairly quick. There should be a good reason that's the case. Something about you that's uniquely really cool or special, or a backstory for how you lived through the apocalypse that's more interesting than "oh I was just already living here before things went to hell, and I heard this group needed a mechanic." I actively want you to be just the special-est unicorn. Seriously hit me up with with "OK so I'm actually the original prototype for the first human-equivalent AI" or "a science lab created me in an experiment so I need you to stat up a unique morph for me" or "I'm actually the lead researcher who created some horrible doomsday thing you need to now make a huge focal point of the campaign." And I totally want to have to stat up the assassin that's been on the hunt for you and oh yeah you actually used to date or whatever too. I'm planning to run a pretty improv-y game, in a very "yes and" sort of way, and even if I wasn't EP is kinda built more for everyone being really exceptional from the start as opposed to D&D liking everyone to start as humble dirt farmers who become demi-gods by grinding through hordes of monsters.
On top of having a cool backstory, you should be just stupidly good at at least one thing. Eclipse Phase doesn't have character classes, but it shovels so damn many skill points on you that you kinda have to try to not be stupidly good at at least one thing, and as a game that has has some roots in Shadowrun, it runs very well when the party has a Heist Team sort of thing going on. As a GM my life is easier when situations just naturally play into stuff like "Right, so we need the thumb drive with the design specs to J.K. Rowling's orbital weapons platform in order to disable it. Squiggles, you sneak in through the air vents and disable the cameras. Ferdinand, forge us some invitations to the fancy gala ball... and to be sure we can get out of here after, Brianrietta? How's about you try and seduce one of those trucks." How things actually play out in game will obviously be much less silly than that (or possibly exactly as silly as that) but the point is, everyone should have a different cool specialty they bring to the table.
Making characters and other nuts and bolts stuff...
In my experience, actually putting an Eclipse Phase character together is pretty quick and easy in 2nd edition. I've seen a few fancy online character generators but they're really cumbersome with awkward outputs, so I'd suggest just using like notepad or something for character sheets. Here's literally what I'm using in a game right now.
Mechanically, Eclipse Phase is super simple, really. You've basically got a skill for everything, with a percentage next to it. You wanna do that thing, you roll dice that give a result from 00-99 (and yeah that's slightly different from how every other game ever handles a d100, deal). If it's equal to or less than your percentage in the skill, you did the thing. If it's higher, you failed to do the thing.
And of course there's stuff that modifies the number you're trying to hit, like if you're using just the absolute fanciest top of the line microphone to record your ASMR video you'll get like maybe a +10% bonus, or a -10% penalty if a laser cannon just shot a hole through your torso. It's a crit if you roll doubles (11, 22, etc.), and things can also be special if you roll over 33 or over a 66. And like if I'm trying to shoot you and you're trying to duck out of the way, we both roll and if we both succeed, high roll wins, like blackjack. Crits take priority over rolling high, and if it wasn't clear, these various extra special things amplify both success and failure. Rolling a 77 is super great if your skill is 80%, but extremely bad if it's 75%.
There's also these things called "pools." You mostly get them from having a rad morph (or body if you prefer). Cram your brain into some genetically engineered Fist of the North Star bod or like a Terminator, you get lots of points in your Vigor pool, you can use those to do a few impressive macho things, or modify related die rolls in fun ways (like spending one to flip the digits of a roll- turn that 94 into a 49). This is the main thing that represents what a morph does for you mechanically. If you're like, super practiced at pole vaulting you're good at it no matter what body you're in, but you know, give someone giant grasshopper legs and even if they don't know what they're doing, they've got points to play with the dice and likely pull something off. Oh and I'm using Vigor since it's the easiest example to picture, but a kind of freaky conceit of the game is that you DO use the brain-meats/CPU of whatever your mind is stuck inside, which also affects pools for doing math in your head, or having good social skills.
Also worth noting- "Loot" isn't really a thing in Eclipse Phase. It's a post-scarcity sort of setting, so in theory, if you want some big laser cannon or a super high quality microphone, you just find a schematic for it, dump some metal and plastic into a 3D printer, and wait a few minutes. In practice, there's headaches because if you're way out Rimward all the metal and plastic available is probably being used for important stuff like life support or bulkheads or someone's weird art installation they aren't ready to take down yet, and if you're Sunward, there is super aggressive DRM for just absolutely everything. But that's still generally good enough to treat all your cool cybergear like your Steam library. You leave everything on the server except the stuff you know you're gonna be doing stuff with soon. In game mechanics terms, there's a few abstracted mechanics and some hand waving that basically say someone is going to have you hooked up with all the stuff you need for your main area of expertise and general purpose handy-stuff-for-PCs-to-have and if you find yourself really in need of anything past that, you can generally ask around online if you're in the right circles and borrow/have printed anything else. Which means you don't have to (and shouldn't) obsessively grab everything not nailed down and stuff it in a big sack.
Kind of related, I'm planning to keep to like a 60/40 split of adventure locations where the campaign starts and exotic far-off parts of the solar system. The standard system for long distance travel is called Farcasting, where you just upload everyone's brain to the internet, beam it across the solar system with lasers and such, and download it into a loaner body at your destination. So, whatever rad comfy morph you start off in, assuming you don't get it killed, you will get to be in most of the time, but sometimes you have to just deal with what's at the rental place and the associated dysphoria and distress. So you can have a character who's just really 100% all about being an experimental totally unique sparkle dog from Sparkle Dog Labs, but try and have enough of an inner life that you can deal with just being the mind of a sparkle dog temporarily inhabiting the body of a sexy robot or a sassy octopus or whatever for a quick trip to crash a fancy wedding party on Venus where they don't have a branch office now and then. Also this kind of a house rule but I figure the default deal is the travel agency rents your body out to someone else until you get back if you don't cut a special deal and you maybe come home to a weird haircut or a scar or two you didn't have before sometimes.
Drifting into baseline vibe stuff and house rules...
There's a couple odd little lore/mechanics disconnects that bug me with the whole resleeving to different morphs thing from where I sit.
One is that having any sort of physical body at all is cannonically super rare, but PCs don't just have access to them, but also backups if things go south or they're traveling, and wide selections. That one I rationalize with "hey, you're all very special with very in demand skills doing very important stuff." The other is that actual meat bodies are more way more rare and in-demand than robot bodies or pods, but that isn't reflected mechanically, like, at all. So my personal headcanon/house rule is that A- when you're morph shopping you're focusing on the real top of the line robot bodies with much worse ones not listed in the book, and there's some less practical upsides to being made of meat, like you have actual nerves and taste buds and such which give you the real senses-having experience as opposed to robots where like sure you have a sense of touch, but every time you grab a sponge you get the same stock sense-memory playback as every other sponge and it's super noticeable like when you hear that one door opening sound Doom used.
And just because for some reason it's the one thing in the rules where everyone who reads it seems to picture something different (especially when they see the words "shape adjusting"), so let me break down the clearest illustration that's been put out for them:
If you look closely here, this weird lumpy fellow is basically like 9 or ten of the same vaguely chicken tender shaped box latched together with spindly little arms popping out of tons of panels. Still a bit visually confused, but you can kinda see how if you wanted you could disconnect them from this SORTA humanoid shape and instead string'em together as like a big long snake, or how you could disconnect one and it'd have panels that'd slide open and extend a full set of 4 little doggo legs and run off and do it's own thing. I'm not saying ALL flexbots are confusing chicken tender modules, probably more common for them to come in cube or cyllinder cases, maybe dodecahedrons, but this is the basic idea. It's not like some T-1000 thing, just, modular link-up robots. And yeah they're kind of a headache to actually use as a morph, especially because you have to make fresh dysphoria checks every time you link'em up in a different configuration. For what it's worth, actual go all-flowy and reshape themselves robots ARE technically a thing one might find in the setting, but if so, that's one of them rampaging killbots the SKYNET knock-offs left around and it's probably about to kill you or give you the T virus or something.
I think that covers everything?
I realize this is still kind of a long read, but it beats the whole 430-something page book, right? There's a few other things I left out because they might not be relevant at all (I don't really want to run a campaign getting into the whole "hey look the death robots left some stargates around" thing because... really at that point you're in a totally different game and there's way better systems for exploring weird alien planets than this one. Also psychic powers are a thing. You can only use them if you have a meat brain, and they kinda come with the nasty catch that they're the side effect of PROBABLY generally benign Resident Evil type viruses. Totally on the table if you want to get into them, but you should really read the book to get a handle on exactly what you're signing up for there. I'm also glossing over a lot of details on the whole cyberspace side of things, there being criminal gangs and sketchy corporations that'll make a bunch of spare copies of your brain to exploit and maybe dispose of after, memory editing for both horrific reasons and for like if you want to get over that horrible traumatic event and refuse to just see a damn therapist, lots of other stuff I can probably just introduce within the game when running it or you can look up on your own time or whatever.
So... yeah. Read the above, get a handle on it, then let's like, decide who's playing and make characters and pick a time and such when we have the bandwidth.