dent...

Depends on how deep the dent is and how "creased" it is. Dent Doctor, DentRx or Dent Wizard may be able to pull the dent out without marring the paint. Otherwise, schedule an appointment with a reputable body shop.

Not products, but services. Open your local yellow pages and look under "auto body repair"

A lot of those dent places will come to you to fix the dent. Convenient to have it done at work.

No. That's their "big" selling point. All of those services use some permutation of a giant suction cup to essentially reverse or "pop" the dent out. Some specific kinds of dents will not work with these type of repair services, notably any kind of "creased" dent (where the metal has actually been creased) or a dent where the paint is missing. A simple door ding is a good candidate for the Dent Doctor-type services. Anything deeper, more complex, (type of dent) will require some auto body surgery.

Some have portable liquid nitrogen to supercool the affected area then pop it out with no damage to paint and it's absolutely the same as before the booboo. I've had this done with hail damage and afterward you simply couldn't tell it was ever damaged!

Just get dry ice.

On a hot summer day, after the car has sat out for a long time, hold some dry ice in the divit, and it should pop out.

Plus you might as well try a 5 dollar solution before anything else.