think about your win conditions. if you have a set of actions, run down the list and think about if each action gets you towards your win condition. if only one of them does, do that one. if multiple fulfill your win condition, do the one that has the least risk for the most reward.
ex you have a kog comp with a lulu mid and nautilus top.
your top priority is snowballing that kog and keeping him safe. lulu doesn't need ganks, naut doesn't need ganks.
you can either counterjungle the enemy jg and keep them pressured and prevent them from ganking, or you can just camp the living shit out of bot.
later on in the game, you can't decide if you have to group or splitpush or siege or do baron. think about where kog fits best, and do that. kog is your win condition in this comp. play around him.
ex2 you have a poke comp
your win condition here is grouping up around towers and poking the enemy out. your top priority is making sure your primary poke guy (maybe a corki or a varus) doesn't fall behind early. after you've all grouped up and are poking towers, your job is to zone the enemy team and keep them from hard engaging your pokers. it is not your job to hard engage and dive the tower. it is not your job to walk up and try to hit the tower, and then eat CC and die. just zone, threaten, and then disengage when necessary.
i could provide a million individual examples, but the idea is to think first and foremost, "what's the most likely way I'm going to win this game?" and then just play around that thought constantly. if a certain action would be counterproductive to that win condition, don't do it. don't call for splitpushing with a kog comp. don't try to do baron with a poke comp (unless you killed the entire enemy team). don't try to do things that don't give you very much towards your comp and win condition.