Hi MCFC & welcome to SimV,
The best place to look for info on Joining a VA is here =
The Virtual Airlines Forum, right here at SimV, there's always lots of VA news in there. Either that or just 'Google' 'Virtual Airlines'.
Each individual airline will have it's own rules covering all sorts of things like how often you need to fly, how much experience you need before you can join (some require a bit of experience & knowledge), some VA's require you to use their own ATC, it goes on & on, there are also airlines that you need no experience to join & some when you can just fly whenever you like. But rest assured, with so many VA's out there you will always be able to find to suit yourself.
Three good ones are:
Tradewind Caribbean Airlinesor
Bush Flying Unlimitedor
Margarita Air ClubHope this helps,
TSC.