How to win Summoner's Rift:
gain advantage - kills (jungle ganks), farm, buffs, turrets
keep pressuring after getting the upper hand - time dragon, baron, force team fights you know you should win, and take opportunities that are advantageous.
control enemy team - wards, CV, champ specific spells, don't let the enemy get on equal footing.
make as few dumb moves as possible so you don't loose your advantage.
My take on SR, might have forgotten something.