i make rollerblading vids(for all u who dont know its the same thing as skateboarding vids just rollerblading) and I see these people roll behind the skater with no camera movement at all.how do you do this?

Two possibilities. A stabilizer (likely). Or a track (too much trouble).

Robert,

An inexpensive thing you can try is a Bogen Super Clamp fitted with whichever quick release plate matches your camera.

You can either clamp that onto the front post of the handlebars of a bike and follow the rollerblader, or clamp it to the back (on a rack) and have the rollerblader follow you.

One thing...bikes with nobby tires jiggle the image too much. Smooth tires on a paved or flat surface (especially bikes with shock absorption) should be pretty smooth.

yeah but i see people have perfectly still shots while holding the cam in their hands and rolling

Most skateboarding videos shot with VX/150 or GL's with the Century "death lens" fisheye set to the widest zoom. the camera is held by the handle and its most common to skate along with the skater basically pointing the cam towards the action.The extremely wide angle with steadyshot allows for a pretty smooth picture.The lens is called the death lens due to the fact that you can get so close into the action thats its very likely you could be hit by a loose board or skater for that matter.i've seen smaller cameras like the sony 900/pd100 attached with an upside down L bracket so that you are basically holding the cam at a low angle as well. "Menikmati" is one of the best shot skateboarding videos . You should check it out if you have a chance it will give you some shooting ideas.

ohhhh I thought the death lense added shakyness

No if anything it would be smoother. I dont know what cam you have but i know that my VX2000 is least shaky handheld at the widest zoom(without WA lens) . complete telephoto you might as well forget it without a tripod or something just way to shaky.

A steady cam is the answer. You need to maybe, be in a moving car, or on a scateboard yourself! [you better be good!]
glenn