What's the best time to use special attacks?

Like the title implies, i'm not entirely sure WHEN is the best time to use my special attacks. I usually save them in case of giant bosses to get a 1 cycle on their weak point meter (cuz they cancel endlag after stuff like link's c4+aerials) but if i'm feeling impatient and strong enough i sometimes use them on tougher foes or to get some enemies away from captains.

Am i doing things right?