hey i just downloaded the world of warcraft demo (up to lvl 20) and i was wondering if anyone had any tips? what would be some good race/class combos? engineering tips, like what to do once ur an apprentice?

Engineering is fun, I would take Mining as my other profession if I were you, It will save you a lot of money in the long run. Most professions don't really bear fruit until you get to higher levels. I wouldn't spend much money on them yet.

As far as Race/Class the benefits aren't super imbalanced either way. Just pick a race who's back side you won't mind staring at for hours at a time.

Well... the class and everything is up to you but the easiest class's to play would be mage or hunter. race doesnt matter what ever you want there. The engineering thing you should not worry about untill a little later. you can however get a gathering profession like mining or herbalism. Those make you some pretty nice cash and are fairly easy to do.