Winterhold: Defense Against the Dark Arts 202

Tolfdir does a reasonable job of teaching novice wizards the ropes, but I thought I'd add a few things.

Lesson 1: DO NOT launch a spell into this.

Unless you're this guy, just hold back the magic and save your energy

You'd be amazed how many times an ally can jump in front of a fireball at the last possible moment. It never, ever goes well.
Either wait until someone personally goes after you or use a spell that chooses it's own targets, like grand heal.
The same goes for when you're travelling with a companion. Take the time to reposition yourself and perform clean shots. Otherwise, just use restoration magic. It's safer than a lightning bolt.

Lesson 2: Restoration is More Efficient than Destruction

If you ask me if I'm a priest one more time, Lydia, the next spell I send in your direction is going to cook you from the inside out.

This is assuming you have a buddy/summon or two to employ healing spells on. A master healer can survive just about anything without losing any magicka at all, whereas a master of destruction magic can still run out of power really fast without doing much damage at all.
I hate to say it, but in Skyrim, destruction magic has a real curve on how useful it can be.

Lesson 3: Wards Are Not Shields

This is what a functioning ward looks like.
If it's transparent, it isn't working.

• Wards drain your magicka faster than you can imagine.
• Wards are only good for stopping spells and dragon's breath. Arrows and axes go right through.
• Wards take about two seconds to charge up before they're capable of stopping anything.
• Never hold up a ward in the middle of a magical duel unless you're charging the enemy or running for cover. You'll lose all the magicka that you should be using to cast fireballs with.
• To make wards work in your favor, wait for the enemy to create their own ward, then summon a spell into your hand but don't release it. The enemy wizard will be too damn stupid to save their magicka and waste it all holding up a ward against a spell you never even threw.

Lesson 4: Always Hit Hard at the End of a Wizard Duel

Don't blow your magicka wad right at the beginning. Most wizards know restorative magic, although they never pull it out until they're really low on health. Don't give your enemy enough time to heal.

Take your time with these sorts of fights, maintain a healthy reserve, wait until your enemy's health bar is at least below 25%, and then unleash your true power.

And remember that when you're holding a prepared spell, you can't regenerate magicka.