Like is it OK to go throttling other players or just stick to the monsters?
Is there some sort of game ettiquette, or is it all in brawl??
Thats the beauty of this game! You can do either or both. At your level the PvP is more of a brawl. Ettiquite comes later when you have more to lose by getting de-leveled
With all the guilds about, which one should you go to?
I'd like to go to a well established high level one but not sure whether you should stick to the low level ones if your new.
Don't take this the wrong way but not all high level guilds are all they are cracked up to be. My suggestion is to find one you feel comfortable in with people that have similar interests. As long as you are not hopping from guild to guild every two weeks, there shouldn't be a problem. If you join a guild thats not right for you, make sure you don't 'burn the bridge' when you leave. Always try to leave on good terms as many guilds have blacklists and share them with their allies.
Hope that helped somewhat.