I remember organizing a ME RP when we still had the old forums (some of you might still remember).
The best we could come up at the time was creating 3 social hubs (to begin with) which were open chats (I cannot remember which sites were used for that).
We had quite a lot of people and it was fun, but the problem was that it slowly died out because people showed up less and less for a number of factors.
So I am going to post some suggestions on how to avoid the same thing from happening again (based on personal experiences).
1. Do not have 1 single person dominate the RP. This happens very often in these situations and it causes beginners to feel intimidated, without a chance to join in the existing RP. This is also a negative because people gets accustomed to 1 person "leading" the general direction of the RP, so when that person is not online everybody else behaves like a Lemming, not exactly sure on what to do.
2.Do not put ridiculous restrictions. If I want to slap your character in the face I should be allowed to do so, and you are not going to give me the Matrix ultra senses of awareness that you can avoid bullets and can sense things before they happen. Telling people what you "cannot do" creates paranoia of what one can actually RP and in the end stops because the mod starts going "No! You cannot look at that character the wrong way, that is God-moting!" this only causes people to get fed up and leave. So let people be free, if you are an a*hole and just go around shooting people for fun, then that person needs to be told to stop or will be excluded from RPing, but until then, behaving in a civilized manner is common sense and most RPers knows this.
3.It is the job of everyone present to make sure of not excluding newcomers, so if there are already established RP hubs or groups, do not just sit and wait, but create opportunities to involve the new arrivals, this gives a great feeling of acceptance and really makes you want to go back every day.
4.If there are people having private RPs (like if they are RPing a private gathering at someone's house, on a mission or whispering) they should move into a private conversation group and continue without interfering with the main hub RP, but do not just log in to go on private RPs, keep showing your face around or the rest of the RP community will slowly wither and fade away.
5.Not all RP has to be about you being a mercenary or the galxy biggest badass, this is a huge universe which has a lot to offer, such as Traders, Crafters, Writers, Engineers, Designers, Artists and so on so be creative!
6. The optimal time frame to RP within ME is the times between ME 1-2 simply because the RP does not have to focus solely on the events of the Reapers or Shepherd and there are more open opportunities to travel and visits different parts of the galaxy.
7. Make sure the direction of each RP HUB is clear: One HUB purely for people to socialize which does not have to be about fighting at all (think of a classy/regular bar), the other for a more rough crowd who wishes to do shady, dodgy deals or are looking for a fight, and a third hub, something tranquil which can bring the first 2 hubs together, like the Citadel promenade of ME1 (benches, green, fountains random people walking by and so on).
8. I do not recommend this but some people prefers to use dice rolls over RPing out a situation. Easiest way, is to do it with a d6, it makes it less random and less complicated, there are a ton of web based dice rollers out there, pick one, and roll your d6, set yourself a target of 4+ (50% chances) to "succeed" in what you were trying to so. In case it is a situation involving 2 people they will both roll, this leads to one person winning and the other losing (or doing a draw). If it makes sense you can even add a modifier like +1 to your roll if it is justified (like your character is punching someone and is wearing some kind of omni knuckle-dusters), but for the love of Shepherd keep it simple.
9. And the last thing, Regarding character profiles, keep them down to a minimal, the point of RP is to discover, learn and evolve a character, if you are going to tell me how did you grow up and what is your favourite colour within your description, what is there left to RP? Just keep it down to simple visual bullet points as a user here has already postedt, this is what the other person "sees" not their history (but it doesn't mean you cannot add details to each):
-Race:
-Gender:
-Body (skin tones for humans or Asari shades, Krogan plates colours etc):
-Current Attire (heavy armour, dresses, gowns etc):
-Specifics (facial Paint? Does the character have a particular scent to them? Any visible scars? Does it look well after themselves? Skinny or fat?):
-Notes (anything which does not fit the above, like OOC advice on how to reproach and warnings on what this user is strictly against).
That's it for now, remember these are only suggestions, so you do as you wish with them 