Don't die.
Also, try other champs, maybe you are more suited to use a tank or bruiser.
About gameplay, learn to play safe, if an enemy is fed (has kills, is higher level than you or killed more minions, (which you can check by pressing the TAB key)) don't engage.
Use wards, try not to go alone in terrain which you lack vision of.
Recall when you are low on hp, buy potions to have sustain in lane.
If you can't vs a champ that is strong early game, play safe, if the other player is generally closer to your turret than his, call your jungler to gank him.
Remember you get more gold from minions than everything, just hitting a minion won't give you gold, you have to deliver the killing blow (if your minions kill the other minion you don't get gold), so pay attention to how much damage your attacks/spells do, and check how many hp the minion has left (do so by clicking on them, and info tab will spawn at the top left of your screen)