Have you ever noticed that some areas are restricted? That if you hang out too long an agent may appear and kill you? Each of those restricted areas has an "Access node" in it. What you must do is aquire an access key(please see above link Ramoji was kind enough to leave to get these locations). Once you have these keys you must then hack these access nodes(again see Ramoji's links). Each access node you tag not only gives you permission to be in that area(haha agents ) but you get major xp. yay!
Hope that helps!
Yeah, that teleporting thing is a lifesaver. Just findsomeone with that and join their team. They can just teleport you wherever, so if they know where the nodes are, you're goldenn. Easy XP.