Constantly ward that bush in the river.
Focus on CS, not killing.
Try and trade effectively, varies per champion.
Keep map awareness. If you can't roughly pinpoint where the enemy jungler is, don't be too aggressive.
Watch the minimap. If your team is contesting dragon, TP in. If you see bot lane is pushed in and they have reasonable health, tp from behind to a ward if there is one.
Understand how tanky you are, especially as malphite. Understand how much damage towers do and if you can dive to assist your team.
CS. Seriously.
Push your lane if your enemy roams and you can't follow. Say they tp bot for a gank and you don't have tp, push as hard as possible. This game is about trading. He trades his lane for the opportunity to assist his team and get kills.
If you get wildly ahead in lane, like stomping your enemy, try and roam a bit. Killing an enemy over and over has diminishing returns and you'll do more helping your teammates that proving a point to your laner. Exception is Nasus. He's not allowed to be left alone.
And lastly. CS. New players think the game is about kills. Then they wonder how they had like 15 kills and lost, but they killed like 50 creeps. Creeps are your gold. 16 creeps = 1 kill