Best way to level destruction?

Destruction magic needs to hit its target, and it depends on the amount of damage done. The more damage you cause, the more experience you gain. Even still, leveling it is especially slow, so you will want to take advantage of all the possible boosts before power leveling that skill:

• Mage Stone
• Lover's Comfort or Well Rested

The best way to do it is to find an essential NPC and roast them for a while. Bonus points if you use destruction in one hand and restoration in the other hand (to level both at the same time!). If you don't want to waste time training it this way, I would suggest getting the rune master perk and using lots of runes while you go dungeon exploring. Runes are fairly high damage and you can cast it ahead of time and allow your magic to regen before proceeding into battle.

Also, here are the destruction trainers, its worth thinking about just paying for the training since it takes so long:

• Wuunferth the Unliving in Windhelm (Common)
• Sybille Stentor in Solitude (Expert)
• Faralda in the College of Winterhold (Master)

I know the most common is vilkas of the companions, but i find it easier to actually pick a stormcloak or imperial camp that is in enemy terriitory (no bounty if say a stormcloak camp by solitude) and each one has an essential commander that cant die and regains health quickly. also in between periods where they regin health you can recharge magika and just leave when your done with no bounty and easy xp for destruction and also can be done at any time inlike the one time with the companions.

The Destruction skill tree actually needs to damage to level up, so doing it on something that is unkillable will work best. Or if you just want to do it on the go, your best bet is to do quests and burn people alive?

If you did the Dark Brotherhood quests you can cast it on Shadowmere, then stop for a few to let him regenerate. Rinse and repeat.