Dying for Free
Recently in my ranked games I have had numerous teammates die for free. Some advice: Stop dying for free.
Oh it's a 4v5 and your adc is split pushing but you think you can win the fight? STOP. Wait for ur adc to split then group up. Oh you outnumber the other team but you have no clue where the other enemies are? DONT FIGHT. Oh there's no vision on the map and you're gonna casually face-check that bush in the river/enemy jungle? Don't even bother until you have vision of most of or all of the enemies.