Support is literally one of the easiest roles to play, and I cry when I see someone be absolutely terrible at it when there is absolutely no reason. If you're going to ward far up the river, let the adc know so he doesn't get suddenly ambushed and died because they didn't know you left. Stay close enough to help but far enough not to get hit without purpose. Know your support, what it can do, what it can't, likelyhood of survival in x y z scenarios, etc.
The minimap is your friend, you should be looking at it as much as the lane you are in to see what is happening everywhere. If your adc is overpushing like crazy, missing last hits, and making a scenario where you are highly likely to die, tell them to last hit as many times as you have to even if they threaten to mute, because they are being dumb and you are correct.
Have a reasonable grasp of what your support can handle and who they can handle it against, especially other supports. I don't sona vs malphite supports, cuz that rock shield is free and i can't keep a positive exchange most times. They might say "Sona is countered by Braum" to which you say "bait the shield, duh." Play about 1000 games a support. Then you'll be good enough.