Since the add-ons have given the "Legendary" option to the skill trees, the level cap has been effectively removed. You can actually now level to the point where you unlock all of the perks (level 252), but it means going from 15 to 100 about 169 times. Of course, you can keep going after that, if you so desire.

My question is, if you wanted to maximize the rate of leveling, what would be the best approach?

There's lots of tricks out there to learn one particular skill fast, but I'm thinking it might be more efficient to find situations where you level multiple skills at once. On top of that, there might be some where you could effectively walk away from the game and just let your character level (ie. rubberbands!).

I'm thinking you could attack a townsguard, then run around and gather them all up. Let them attack you to their hearts content. Equip high defense armor (light & heavy) and a shield and enchant everything with magicka regen. Then just sit back and let them have at you while you cast healing on yourself. This way you could level Heavy Armor, Light Armor, Blocking, and Restoration.

Are there any better ways?

Restoration loop then legendarying smithing and speech.

Illusion and Alteration. Muffle in one hand, telekinesis in the other and you humiliated the leveling system. Remember to get extra magicka itens, cheaper alt/illus/all casting robes and getting cheaper casting perks.

Buy skills and pickpocket them back
Spam Muffle.
Get attacked by a bunch of Mudcrabs and spam Bound Sword and Close Wounds/Fast Healing.
Spam Detect Life in a crowded place.

What's the restoration loop?

Never done it myself, but looking on youtube, it's where you enchant your armor, ring & necklace etc...with fortify alchemy , then with at least 40 in alchemy & some perks, make fortify restoration potion, drink it, remove then re-equip your armor/jewelerry with he fortify alchemy on it, then make an even stronger version & rinse & repeat until it's something stupid like restoration spells are 1000% stronger etc... i assume it works with smithing as well etc.. whatever , sounds boring to me.

Restoration loop

Also read this

http://www.gamesas.com/topic/1480039-enchanting-robes/

Just set the game to novice damage setting and you're done. It takes 3 seconds.

Stupid exploit to ruin game balance.

Get 100% illussion reduction gear, mage stone, and well rested or lovers comfort and cast the master spell harmony in a crowded town. You will go from 15 to 100 illussion in just a minute or two. Rinse and repeat

The Fortify restoration "glitch" as it's often called isn't actually a glitch at all. The values are legit, and works off of the "effect stacking" rule in the code.

The game balance is only ruined if the player takes it to the limit. I only use it to enchant items that give me better magika regen. Other people will use it for one hit kills, riduculous armor rating and basically play like a god where no one can touch you.

I've stopped with the 1-3 hit kill/death playstyle because of losinf too many DiD characters.
I now only use weapons with 200-400 damage (50-100 on legendary) and upgrade health a little bit.

I don't use it to cheat but to make certain weapons useful.

Oh I hear ya. Theres some that take it to the extreme. Im not one of them. And as you know, Im really new to using it. I think the only thing I might use it for is to add to my carry weight, but thats even iffy.

I think I'm gonna use it to get to the armor cap with unmatched armor combinations. It'll eliminate the need to wear a helm.

The restoration loop is fine, everything is fine in moderation and anything in excess can be bad regardless of what it is.