close blast 3, each creature in the blast
Hit: 1d6 + Int mod thunder damage, and you push the target a number of squares up to your wisdom modifier
Piece 1: Thunderwave is a close blast 3, and targets every creature in the blast.
Note: A close blast X is an X-by-X box that does not include the origin square but has at least one of its squares adjacent to the origin square.
Piece 2: Thunderwave pushes creatures it hits a number of squares equal to the caster's wisdom; with a good wisdom and feats/items to boost it, the push distance begins to exceed the typical character movement speed (6) around mid paragon tier.
Benefit: When using a close arcane attack power, you can choose a square within 2 squares of yours as the origin square. The power still follows the rules for close attacks.
Piece 3: Arcane Reach allows you to choose a nearby square as the origin square instead of using your square.
Putting It All Together
- Pick the direction you want to move
- Cast Thunderwave
- Using Arcane Reach, pick an origin square 1-2 squares away from you in the opposite direction from the direction you want to move
- Choose the area for Thunderwave such that it includes you
- Hit yourself with Thunderwave
- Push yourself away from the origin square, and thus in the desired direction
Here's a crude image I threw together in OpenOffice Calc. Hopefully it makes sense (if not, let me know in the comments and I'll try to make something a bit nicer).
How to Get the Most Out of It
- Increase push distance; if you're not getting at least speed+2, it's probably not worth the trouble
- Get some thunder resistance, ideally enough to completely negate the damage from hitting yourself (you still get the push even if you don't take any damage)
- Improve your attack roll; if you don't hit yourself, you don't get the push
- Reduce your fortitude score; if you don't hit yourself, you don't get the push
This trick usually isn't worth it.
Getting the forced movement boosts isn't particularly bad, since they make the power better for its normal use, and improve quite a few other wizard powers as well. Increasing your attack roll is always helpful, so resources spent on that aren't wasted at all.
Reducing your fortitude is generally a bad idea (unless it's already awful anyway). Wizards tend to have pretty crummy fortitude defense in the first place, and if you make it worse you stand a good chance of monsters being able to hit you on a natural 7 or even lower. Thunder resistance, particularly thunder resistance good enough to completely negate the hit, is not easy to come by, and is likely to eat up your neck slot magic item (that being the easiest way to get it).
The real waste is the use of the standard action. You could put the same distance between yourself and foes by pushing them away from you instead of pushing yourself away from them, thus doing damage, repositioning foes to help the rest of the party (your actual job, since you're a controller), and completely avoiding the investment in thunder resistance and the risks associated with reduced fortitude.
TLDR: It's an amusing trick and simple but still moderately interesting theoretical optimization, but in actual play you're usually better off just using the run action.
Addendum: Vertical Movement
The relevant rules text is on page 213 of the Rules Compendium:
Two-Dimensional: Forced movement is normally two-dimensional; all the squares of the movement must be on the same horizontal plane. Forced movement can become three-dimensional when the target is flying, is moved through a substance such as water, or is on a non-horizontal surface, such as an incline, that supports it. This means an earthbound target cannot normally be pushed to a square in the air, but a hovering target can be. Similarly, a target can be pulled down a flight of stairs, and it can be slid in any direction underwater.
Thunderwave won't get you airborne, but if you're in the air already then you can gain altitude with it.