I just went into a battleground for the 1st time, and was confused as he!!; no idea what I was doing. If I go off on my own, I just get ambushed; should I stay with a group and try to defend, or what? And what abilities are good? I'm a goblin, btw.

i like to wait in towers and stuff and only fight by yourself it is 1v1 if there is a group nail the healer. and good spec is mutilate(assassination) use your cheap shot to stun them then mutilate then kidney shot then mutilate rupture if it is a plater wearer and envenom if its a clothy. and meet up with rabid battle monkeyz on hakkar! we can help ya more.

there are planty of great sites with this kind of information available.

Arenajunkies.com
mmo-champion.com
elitistjerks.com

just navigate the forums (strategy section for arena junkies) and read up on it. the people who wrote these guides are very experienced and know what they are doing. check it out. you will get a whole lot more information on those sites than you will get here.