Ah. Well.
First, I would suggest going here. It should get you back up to speed with recent history. See anything you do not recognize/remember? Follow the handy link and/or enter a search term and read all the assorted information involved.
Sadly, while the wiki is comprehensive, there is a lot of information which gets lost in the bigger scheme of things. You want to know more about the workings of Malta's Titans? There happens to be a couple of missions with information you will want, but they are going to be hard to find just by looking at Malta's villain-group profile. Fortunately, a lot of villain-groups have their own individual lore pages separate from their profile, so if you do not mind spoilers, you can get comprehensive info on the group history and major events, if not the individual nit-picks.
For said nit-picks, you can read the mission info - but again, these are sometimes hard to find. If you feel a burning urge to do so, I would recommend looking up Task and Strike Force information, and then from there looking up related regular contact information and associated story arcs.
If you want to consult a lore nerd, I would recommend contacting one of us RP forum-goers via PM with the fine-detail questions.
Alternatively, as an absolute last-ditch attempt, you can play the game. ^.^
Two years, ye say? Well, I have some recommend reading for you to catch up on!
The Second Rikti Invasion and Vanguard
The Return of the 5th Column and Reichman
Ouroboros and the Coming Storm
Incarnates
The Praetorian Revamp and Praetoria the game and Praetoria the world-lore and Praetoria Praetoria Praetoria. In case you did not notice Going Rogue, it is somewhat big now. :/
As for 'how to' tidbits? Well, there is no correct way to RP. Generally the rules can be boiled down to such:
No god moding (No pulling information you have no access to from nowhere, no attacks which hit automatically unless it is for a really good reason, no being completely indestructible or all-powerful etcetera.) A good rule of thumb here: If you can do it in the game, you can do it here - and within reason, you can twist and bend the rules if it makes sense. Sure, you can cast ally-specific buffs on yourself, and sure, powers with normally insane recharge times can be a bit more available.
No auto - Related to the above, no forcing actions. Whatever you put on the table? Everyone else gets to play with it before they decide what it does.
No being a jerk - Really simple. A character can be a jerk, that is just the character, but as a player behind a character you should try get along with everybody. If you have to deal with a complete psychopath, on the other hand, there is this helpful /ignore feature...
Canon is canon. No saying you married Ghost Widow and then completely healed Wretch. On the other hand, RP canon is rather mutable as long as you have permission...
And also: Proper grammar. An honest mistake is an honest mistake, we do not enforce 100% gud spelng heruh. But at least write legibly. (Does not look like that will be a problem. ^.^)
This applies to both forum and online RP. Are you having trouble? Flabbergasted by something somebody else said? Just ask yourself: What would charactername do? Just go with what seems natural and it should all work itself out. And talking to strangers? There is nothing but strangers out there, I am afraid. If you hear something going on in local, feel free to jump in if you see a point of entry. A lot of RPers use private messaging. If you suspect they are, shoot one of them a PM asking if you can join in.
That being said, welcome back, and welcome to the RP forum. We have been expecting you. 
Also, forgot to add: Feel absolutely free to jump into any threads below marked as 'open rp.' It helps to read the first few posts to get a general idea of what is going on before you do so, of course. And when it comes to the mind-boggling, reality-shatteringly RP-Forum long-runners like the Whitmoore Apartments, you may wanna contact the thread OP or the most convenient person to ask them what the heck is going on. Bwerp knows, you could dry your eyes out and turn into a zombie before getting through over a thousand pages of posts. :P
Shorter, newer RPs are obviously easier to jump into. Toward this end, I would recommend looking into this RP here. It is brand spanking new and looking for more.
Hello, I recently returned to the game after a 2-year hiatus and wanted to get into RP since I transferred to Virtue. Unfortunately, I know nothing about the world of CoH/CoV outside of what tidbits I learn from quests and I'd rather not jump into serious RP without knowing some history and common knowledge.If anyone knows some resources for lore or can share their knowledge with me I'd appreciate it.
I'm a bit shy with walk-up RP so some pointers on how to RP with strangers would be great too since all I have going for me at the moment with my main is watching the dance floor or "playing" pinball in Pocket D.