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How do spells affect skill leveling?
I am just curious, what factors are taken into account for leveling up a skill?
For example, I just summoned Atronach 5 times in a row, but the Conjuration bar didn't move a bit. So under which circumstances do I level?
Skyrim is not like oblivion they caught onto such things so when you cast a spell it must do something so to level up conjuration you must engage in battle with your Artronach. AFAIK the only spell that you can cast over and over is "Muffle" a second tier illusion spell that "Muffles the sound of your footsteps" so you can spam that while arround NPCs and lvl it.
It seems that the skill needs to be useful to be levelled. Casting armour without entering combat does not reward. Healing when health is maximum does not reward, etc.
As the other posters stated, the spell has to be considered useful for it to count for leveling. What that is means seems to be specific to the school and the spell itself. You can, for example, level the Restoration tree by healing yourself while standing in fire. If you put on robes you may be able to outheal the damage and maximize your time leveling. As your skill in restoration gets stronger you'll needed a deadlier trap to stand in.
Alteration can be leveled by standing underwater and using the water breathing spell.
