- play a shitton, find out which role you are most comfortable in (offlane, mid, carry, support, although supports aren't really seen alot in newbie games) but please, do not play the difficult heroes (invoker, meepo, earth spirit etc.)
- use the mute button. helps a lot, especially later on.
- after you get the feel of each hero's skillset and role, try to watch some professional games. they're fun to watch and the commentators could give some insight into the game, too.
- play with friends, voice chat highly recommended. helps cheer you up whenever your team is losing
- have fun, don't play to win. you won't be angry often (aside from the occasional feeder)