People Tend To Forget

Even I do it a lot in my games. You need to be constantly looking at your minimap. Keep track of their botlane went back or not. Whether mid is missing or just went back. Yes it's nice to have the other lanes ping you if the enemy is missing but it's still your job to be looking at the minimap.

Remember they are 5 players on the enemy team. If you see the enemy team zerging your team try to make the best of it. Take a tower or something and for gods sake if you are outnumbered even 2:1 be careful. If you have to give up that inhib do it. The later the game goes on the more important your death is.

tl;dr pay attention to your minimap at all times. Ward up, play smart.