I agree with the consensus that you should not drop the slide on an empty chamber, but I totally disagree with those of you who think you should ride the slide forward when chambering a round.
What do you think happens when you actually fire the weapon? The slide goes all the way back and comes back forward with the same spring force that is used when you pull the slide all the way back and let it slam home to chamber a round. There is no difference.
IMHO, if you ride the slide forward, you increase the tendency for the round to not chamber properly and it is a bad habit to get into if you use a semi-auto pistol for self-defense. If all you use is a revolver for self-defense, then I guess doing all sorts of weird things to your autoloaders won't impact your training. Just my opinion, but these kinds of bad habits may get you killed if you have to use your gun in self-defense or if you use your gun for your work- e.g. military or police.
I also always rack and release the slide manually rather than using the slide lock lever, as it is much easier to manipulate the slide manually in times of high stress than to locate a rather small lever on the side of the gun.
Just my $0.02.