Good advice here.
Ideally your team will make it easy for you and you'd have backup close by if you got caught warding deep. But that's rarely the case.
Generally I don't wander too far from teammates. If they are focused on the top side of the map, then I'll be around up there, warding baron and sweeping. If a fight breaks out, I'll be nearby to assist.
If your team fights, help them, even if you don't agree with the call. It might work out anyway. But if you don't help, it's more likely they will fail and you cannot stop a push by yourself most likely.
Once laning phase is over you aren't glued to your ADC, roam and help your whole team.
The more you play, the more it starts to make sense. Look at your minimap, if players show top side and you are bot, you can recall and answer, or take stuff bot side. As you keep playing you get an instinct. You'll make decisions, maybe not totally understand why, but it will just feel right.
Make sure to track who is getting fed. As Tahm Kench I wouldn't try to duel a fed Zed, but if he's not ahead, I can usually take him.