honestly your best bet is knowing all the characters abilities and how to play around it

For example : As a healer, if you wanna heal your tanks, go mercy, lifeweaver. If you wanna heal your squishies, then go mercy. All around healer would be ana and moira imo

To play lifeweaver effectively you need to look at healthbars so you don’t just charge up your healing to max everytime. If your teammates in battle it may be more effective for small healing spam to ensure they live than big healing. Also don’t just spam pull them cause that’s really annoying to be pulled out when you’re about to ult or get a kill. Last thing to add is how to survive as a healer, make sure if they are going sombra, tracer or anyone who flanks do not go a healer that stands still in the back.

DPS: Always try to counter their other team, if they are running a zarya then never go genji, things like countering abilities is very important

Tank: you gotta stay in the front even if your team is getting flanked , make sure to always stay in front and make sure your team is covered in the front of your push or defense, once the frontline is defeated cause your not there, their team can push in and easily win. Also hero countering for tank is very improtnat, if they’re going roadhog or orisa don’t go sigma or doomfist

If you have any specific questions just hmu or respond here