I'm playing Skyrim as a mage, and I am wondering how I can level up the skills for mage.

Alchemy and Destruction seem quiet straight forward. However, many skills consist of mostly defensive spells: how do those effect skill progression?

For restoration, I notice healing gets increases my skill; does this only work if my health isn't full?

What about spells that create something (a light, armor rating, a weapon, summon, etc): when will those affect the skill? Does constant renewing increase skill, or is it useless?