I reccommend you watch Purge at : http://www.youtube.com/user/PurgeGamers
Look for his what to buy and laning guides, also watch his games with some of the heroes ( but dont just accept he is god of the game, just pick up tips and learn your own style ).
Grow a thick skin and ignore the majority of what the others players are typing, many rage for the stupidest things and believe they are the ones who will carry the team and deserve everything ( even in a 5 carry team ).
The most rage inducing part is the last hitting and denying mechanics, now that you can practise with against bots... dont try win against bots just try get lots of last hits and try deny a few, get used to the flow of laning and the shopping mechanic... get that right and its all a lot easier then.
Sometimes keeping an eye on your stats is not a good thing
Some things are painfully obvious, others must be made obvious... painfully