If the pistol is empty, magazine out, then pull the slide back and ease it forward. This is especially true of M1911's that have very fine sear/hammer engagement surface dimensions. A slide slamming forward on an empty chamber will cause the sear surface to bounce/drag a little on the hammer engagement surface, slowly rounding the sharp edges of those surfaces to the point the sear will no longer catch the hammer and the hammer will drop to its half-cock notch.
Why does this not happen during firing you ask? Because during firing the trigger is all the way to the rear and the sear is held in position by the disconnector, preventing it from moving.
Why does this not happen when chambering a round from the magazine you ask? Because of the friction of the slide dragging a round out of the magazine and then the bullet is forced up the feed ramp and into the chamber. That friction is enough to slow slide and "cushion" the impact of the slide on the barrel.
Should you use the slide lever to actually release the slide? On this you will get different opinions. In order to have the best chance of getting that first round to chamber, pulling the slide to the rear and then letting go does compress the recoil spring a little more and gives the slide a little more momentum going forward. So ideally, always pull the slide to the rear and let it go in the so-called "slingshot" method of chambering a round.
Can you simply put your thumb on the lever and drop the slide to chamber a round? Yes and I did it all the time in my days of USPSA competition. It's faster than the slingshot method and I ran a shock buffer in my competition 1911, so there was not much more rearward movement of the slide if I pulled the slide all the way back.
Should you keep your hand on the slide during the loading process, aka "riding the slide"? I don't think it's a good idea as it slows the slide and is more likely to induce a feed jam.
