I have played Infected for a while now and I have some tips I want to share with you.
When you have 10-17 surviors stay in a group of at least 3!
When you have 1-5 survivors stay as far away as possible from other survivors as they can be a threat to give up your current hiding place.
When infected place a Tactial Insterton near your enemies and kepp respawning until they are dead.
When Infected form groups to trap people!
Let other players pass you if you encounter any as a survior!
In Arakeden, stay away from the action! (BURGER TOWN)
Don't get cornered when a juggernaut.
Don't run into multiple enemies!
That is all the tips I have for now got anymore I missed comment below!