most importantly as a support, map awareness and the timing of nc pulls.
dont let the stack goes against your objective which is to pull enemy creep lane towards ur carries potential farming capability, if playing safelane.

always, and i mean ALWAYS carry a tp incase any lanes opponents tries to dive, you can counter them with tp's to avoid further more team clashes. one tp cud save lives in this game.

after map awareness, warding and dewarding could pose a threat or a lifesaver in certain circumstances. if warded properly, you get vision of nc/safelane/midlane opponents and to know what item they have or going for, lvl disadvantages etc...dewarding is only necessary when doing the action doesnt pose a threat to you. if you feed, your giving enemy advantage.

bounty and other runes: try to avoid giving enemy take runes if possible, no matter what runes they are.

sod clashes and rs timestamp is also very important for support's task.
buying dust when appropriate and when to decide to buy sentry's are also very crucial for supports when dealing wif invi heroes.