What you do is hit the slide release with your thumb on your right hand while pulling the slide to the rear with your left hand. You will notice that the tension is released on the the slide stop/release and you can let the slide go forward. Be sure to KEEP YOUR FINGER OFF THE TRIGGER, while doing this. (Me, being a lefty, I do it reverse but use my index finger on my left hand.)
There are 2 trains of thought on letting the slide slam forward. Some old timers have told me that with 1911's you don't want to stage the recoil spring and that it's better let the slide close on it's own force, (once you've done the above) because the spring can bind/get tangled by you controling the slide. With newer guns that have full length recoil rods I don't know that is an issue anymore.
The other train of thought is that if you are handling someone else's gun, ie in a gunshop, etc., it's best to error on the side of caution and handle other peoples gun gently, and thus ride the slide closed after performing the above technique.
I think that shooting the gun has to be worse than letting it slam closed on an empty chamber.
However I do agree with what I think the other posters are saying, the slide stop/release is just an aid and should only be used when absolutely necessary. To clarify, when changing mags from slide be locked back empty, I find it's better to pull the slide to the rear and release it, thus letting the spring use it's full travel to close the slide on a new live round in a fresh magazine.
When my Kimber was 1st still breaking in I found that locking the slide back and then hitting the slide release to close the slide on a live round would cause the gun not chamber fully. Pulling the slide back and letting it go on it's own tension made it fully chamber the 1st round.
Well sorry for the long post.
Edit#2 What the guys are saying above is true, don't hit the slide release on a locked open, empty gun, with the magazine in place, to close the slide. Things like to wear when you do that. Once in awhile is fine, say if you are in a shooting competition but over and over is not good.