OK, this is by request...
Prepping your cigar is a ritual, and an integral part of the smoking of a really fine cigar. There are as many methods of accomplishing this task as you'd care to find, let's look at a few of the favorites...
1) The punch- A punch is a little circle of steel designed to put a hole in the end of a cigar. Most seem to be 6-8mm in diameter, though I have seen extremes varying from 4mm to a whopping 10mm! To use this, you hold the cigar and push the blade into the end cap of the cigar. This method does not work very well on torpedoes, for obvious reasons...
What I tend to do with robustos, toros, churchills and the like is to wet the entire endcap with my mouth. This helps keep the endcap from splitting when you punch it. Once you've moistened it with your tongue, let it sit for a couple minutes. Just before you punch it, moisten it again, then with a twisting motion, gently push the blade into the center of the stick. It doesn't need to go very deep to get a clean punch. Twisting as you remove it, you should be left with a neat, uniform little circular hole. Now draw on the cigar a couple times. This lets you taste the raw tobacco, and also lets you know if it is wrapped too tight (lots of resistance to the draw), or if it is too loose (almost no resistance, will burn hot). If you feel like you're trying to suck a milkshake through a straw, it's too tight. They make something called a "draw poker" to help this- it basically is a rod that pokes a hole through the length of the cigar.
2) The guillotine- This method utilizes a blade to slice off the end of the cigar. I usually reserve this for very slim cigars, or for torpedoes. There are two basic kinds of guillotines- the single blade, and the dual blade. The single blade is usually a very cheap plastic body with a finger hole at either end, and one angled or curved blade that passes through the middle hole. They're OK, but a much finer and more accurate cut can be made with a dual blade. The dual has a blade attached to each finger hole, when you put the end of the cigar into it, the blades slice from both ends. Most nicer guillotines are of this type.
When cutting the end, put the end cap into the guillotine just far enough to get a good cut. Maybe 1/16" should be good enough. The idea is to slice the end of the end cap, not to remove an inch. The end cap has a gum on it that holds the wrapper together. Try not to cut below the first ring of the end cap, or you'll be trying to rewind your cigar, and that's no fun at all!
Another benefit of this type is that you can cut through a cigar and relight it if it runs down one side, or if you just want to save some for later and want a way to get a clean cut, removing the cherry, this is it.
3) The Cigar Scissor- This looks like a very short pair of scissors with curved blades. It basically does what a guillotine does, but its advantage is that it can handle larger ring gauges. It is also very precise if kept sharp.
4) The Notch Cutter- This looks kind of like a weird stapler. It has a blade on the end that cuts a V-shaped notch into the end of the cigar. I don't see these very often, but some people swear by them.
When using this, you place the end cap of the cigar against a stop, then press down on the bar containing the cutter blade, which slices the notch into the end of the cigar. Advantage- supposedly quick, leaves most of the end cap intact.