Multiple guns also keep practice sessions from becoming a chore. I know that, ideally, you'll find a buddy to come along, or you can blackmail a spousal unit. But I also know that few things in life are ideal, and my spousal unit has agreed not to ask me to any more of those awful period piece three-hour costume movies staring Daniel Day Lewis if I don't whine for her to go to the range with me. When you're alone, practice can turn into a chore, which is very bad for your practice. Something different might be a gun I haven't fired in a while, a test gun or someone else's pride and joy that's just visiting.
Groups are the fundamental building blocks of handgun shooting.
The target distance depends on how much I've been shooting, my mood, whether the range is indoors or outdoors, etc. Suffice to say that unless it's a dedicated bullseye practice, I don't exceed 15 yards. I like to shoot five groups of 10 shots, and I try to make everything in the world go away except my front sight. Starting at seven yards, I'll shoot a group to make sure the gun is there, then progress to one-shot draws. If I can't come from the leather, as in most indoor ranges, I'll lower the gun to the table top between shots.