If you aren't registered on Rockstar's Social Club, sign up here:
GTAGaming has an open crew at the social club, if you aren't in you should join us:
We will host events to play online together. Being in the crew means your individual score contributes to the GTAG total score, no matter what console you play on. There are several in-game perks for being in the crew such as cars, weapons, shared safehouses, etc. More details on this to come after GTA V is officially out (Oct 1).
Here is a list of usernames so you can play GTA V with fellow members from our forums. Post in this thread if you want to be on the list.