Like the guy before this said(and I shall second) this game is all about patience. Harass and slowly take down the ones who you are lanning againsts' health. Make them hurt and they will either recall and loose valuable XP or they will be stupid and stay around too long and get taken out. Stay back early game even if you are a tank(as no tank is really a tank till mid game at the soonest). And get skype and vent. Find a group to play with and use voice communication(skype is best for this game IMO). With voice you can communicate ganks and MIA's much faster and not have to take the time to type when you need to have your fingers engaged in a fight.
"Work harder!! Millions or people on welfare depend on it!!!"