Here's how we straighten them back out in a hurry, or make "taco-ed" bike wheels from the bike shop's dumpster usable again.
This wheel is pretty bent. Notice how the joint is even coming apart.
Pix by Star
Step 1: Find a Hole
As they say in Venezuela, "En tiempo de guerra, Cualquier hueco es trinchera."
I guess the city is planning to plant a tree here. In the meantime it's a good place to fix a wheel. Here I am uncovering the hole. Remember to cover it up again, this is a litigious society.
Step 2: Do the Stomp
Just go for it and stomp it flat.
Extra points for yelling and gesturing.
Step 3: Overbend
So you have to bend it a little further than straight.
Put one or more sticks under the low spots and stomp again, a little more carefully this time.
After a bit of this the wheel will be mostly straight.
Step 4: Spin and Eyeball it
You can mark them on the side with a pencil if you want.
Step 6: Knee Technique
The wheel is now straight enough to ride again.
If you want it totally straight, now that you've got the tight kinks out, use a spoke wrench.
That only works if you've gotten the tight bends out.
Messing with the spokes is for gentler bends.
Tighten the spokes to move the rim toward that side.
Loosen a spoke to let the rim move away from it.
Hit the the spokes to make them ring.
The pitch of the tone you hear tells you the spoke tension.
If the spoke tension is totally non-uniform the wheel will get bent again just from riding it.