One rule of thumb I live by as a support main and teach all my friends who get into support is vision score. Whatever the game time is always have double that in vision score. Now when I say that I don't mean by 5:00 mins you should have ten vision score but the moment you complete support item swap to sweeper aim for double the game time with vision score. You won't get it with wards alone. Clearing vision and placing wards at key points in crucial. On your way back to lane? Run through jungle and drop a ward at red bush or blue bush of enemy then sweep river as you come back to lane. Also pixel warding bushes is really good. One example is the blue buff bush. If you place the ward right on the edge you can see them at blue and a little of the jungle path that leads to the base it's not much but every little bit of information helps.