You can either add people to your friends list, or create a private match in game and send them an invite there. The problem with the latter being you don't know if they are online or not to actually receive and accept the invite.
So first thing, add them to your friends list.
Go to the very right option of the XMB (Cross Media Bar, or your Menu on PS3), once you are signed in of course. Go up to the 2nd from the top option and select '+ Add a Friend', click 'ok', in the 'To' you enter the ID from one of the above or the PSN/XBL id list thread, enter a message if you want to let them know you're from BigFooty and then select Send.
2nd thing to do, once they've accepted the invite, or if you just want to send an invite to someone from the game without having them on your friends list.
On the AFL Live menu go to Online, then to Create Private Match, Press X, then wait until you've entered a lobby and the option comes up down the bottom to hit square, then hit square. In the To section you want to either select from your friends list or if you just want to invite someone not on it you select 'Enter Online ID' to which you enter their PSN and then just select Send.
There, that just about covers it all.
Thanks heaps for the help everyone.
Lopoint forward to playing a game without someone quitting...
