There are a few things you should avoid doing as a noob, and here they are:
#1 Don't try to Ninjaloot - This means a player or group of players killed something, and you are attempting to steal the loot on the corpse. This usually happens when a team is deciding how to distribute the loot. Be aware that players CAN log the fact that you stole something which you did not earn and /petition you.
#2 Don't train - This means that you have a number of mobs (hostile creatures) chasing you and that without warning you pull them through a player or group of players to try and save your own skin. This is something the community as a whole frowns upon, if you can't handle the action...don't go and get innocent players killed if 30 mobs (thus the term 'train')are chasing you for making a mistake. Players can also /petition against you for training, so I strongly advice against it. The most common places this happens is in Temple of The Three Winds and at P7/SB Hecklers spots in Elysium.
#3 Don't beg for credits - That last thing you want to do, is tell someone 'can I have some credits? Im new', you may get 10-100k from a few people, but those who know the game will rather tell you how to make cash rather than give it to you. It would be best for you to search the AO Official Forums on how to make cash at your level. Ask in the forum of your respective profession for more detailed help on making creds. If you can't post, you can still search and also ask in-game in the OCC channel for advice.
#4 Don't try to cheat people in trades - This is possibly the worst thing you could ever do. Trading empty bags claiming that they contain items for cash will get you a fast /petition against you and the game does keep logs of transactions. The community dislikes these type of players with a passion, and you will not make any friends once the word is spread. You also risk getting your account suspended or banned. This is a serious offense in the game.
I think these are the top 4 things to avoid doing if you want to have a good start in Anarchy Online, and remember...have fun and don't stress over the little things in life.