What not to do:
Do NOT fix the generator.
Do NOT fix the generator, then turn to heal the other person, thinking that is the best time to heal up.


What to do:
Go behind some trees or heal each other up first. Then work on the generator together.



The reasoning here is pretty simple:

Those generators make a lot of noise and a visual warning for the Killer when you turn them fully on. At that point the Killer will most likely be on his way to find you, and you won't have time to heal.

When wounded you go down in one hit, no adrenaline rush to help you get away either.

When wounded you bleed all over the place and leave blood trails.

When wounded you make a lot of grunts and groans which can give your position away.


This guide applies whether someone else is injured, or you, or both. If another survivor comes up to you and tries to get your attention (crouching or moving back and forward), pay attention, they probably want to be healed or to heal you.

You can't be healed while working on a generator.


UPDATE: I'll add that this also applies when you're being chased by another player, they probably don't want to chase you all across the map, stop somewhere so they can heal you.

Also if you don't want to be healed (heart beat, or any other reason), you can tap/hold shift to sprint away from the medic and that will break their hold on you. (Check comments: I don't know at this point if that causes an agony scream or not, since I haven't tried it yet).