Depends how useful the ally is to me.
Important ally (someone I plan to stay allied to throughout the game)
1. Support them in all wars
2. Rarely give them anything in peace deals, as I tend to make sure such an ally doesn't have interests that conflict with mine
3. Help with their rebels if needed
Normal ally (someone who I don't mind if the alliance lapses, but have no desire to fight with)
1. Support them in all wars, until they get into a war that isn't worth my effort to save them
2. Rarely give them anything in peace deals
3. Ignore their rebels
Temporary ally (someone I plan to eat later)
1. Support them in wars until I'm ready to turn on them
2. Give them land to keep them sweet until I'm ready to turn on them
3. Ignore their rebels
Important ally (someone I plan to stay allied to throughout the game)
1. Support them in all wars
2. Rarely give them anything in peace deals, as I tend to make sure such an ally doesn't have interests that conflict with mine
3. Help with their rebels if needed
Normal ally (someone who I don't mind if the alliance lapses, but have no desire to fight with)
1. Support them in all wars, until they get into a war that isn't worth my effort to save them
2. Rarely give them anything in peace deals
3. Ignore their rebels
Temporary ally (someone I plan to eat later)
1. Support them in wars until I'm ready to turn on them
2. Give them land to keep them sweet until I'm ready to turn on them
3. Ignore their rebels