Also known as the Dolphin.
There are about 4 different worms.

First of all make sure you always have your shirts tucked in. Guys, never do the Worm if U got a boner or else itz gonna B really painful... And Girlz just watch out what's goin on around U...

#1 Da Original Worm

1) First you start out in push-up position on the ground with your whole body touching the ground.
2) Swing your legs and thighs up putting your weight on the waist up.
3) Push up your arms while your legs go down so the space under you flows forward.
4) Repeat the steps.

It may look like you're humping the ground unless you do it right. It's easy to learn but difficult to master.

Once you get better at it try moving side to side by tucking in your right elbow and going left to right make sure you land on your side or else you can't get enough momentum for a second one.

Also try using one hand. Use one hand to grab your shoulder then try doin werms. If you're skilled enough try the superworm by putting your hands in front of you like superman does.

You can practice by lifting your legs and putting your weight on your hips and chest.

#2 Backwards Worm

It starts like #1 but instead of lifting your legs you lift your shoulders up until it reaches your hips then you use your legs to hop up, use your arms to move backwards and your chest goes down before your legs.

You can start this by going from a dolphin dive it's kinda like a falling handstand where you slowly move down towards your chest then to your stomach then you do the backwards worm.

#3 Flying Worm

This is a bit like the rubber band or jack knife (whichever you call it) but instead of jumping back you roll back on your back then jump out again. Just do Azn get ups then roll back on your back then do another Azn getup.

#4 Spazam Worm

1) Get on your back and lift up your shoulders then when you put your shoulders down you lift up your legs.
2) You should land on the lower portion of your shoulders and jump when 2/3 of your back is up. This should look like an upside down worm.

It might help if you grab the back of your thighs or slap the ground for height. Just make sure you do it fast like you're having spasms.

I recommend you try the first two, they the easiest.