There are a few options on how the stamp will imprint. They make metal and plastic stamps that you press, stamps that you use a mallet with, and even stamps that you brand (electrical heat).
The least expensive are the plastic variety that you use some sort of press with. Most common presses are a c-clamp, arbor press, drill press, vice or whatever you have that can apply a good amount of pressure. I can only speak to this type as it's what I chose.
The place I got mine did a great job of getting very good definition on the font. It's a very clean impression with a font that is fairly complex.
Things I like are that it works well, it was inexpensive and seems plenty durable for the job.
Things I don't like, it can be difficult to place perfectly (I've marked the back side to help), I use a piece of wood on either side so that the damp leather doesn't get marked by the steel of whatever I'm using to press with which can be difficult. I chose a stamp a tad too large. The large size, I'm sure, is at least partially responsible for the great definition, but it doesn't fit on every sheath. I'm going to have a 1" stamp made, and I'll ask about maybe going with a different font in case the designer thinks that might be a better option for the size.
If I had to do it over I'd go the same way, but a bit smaller. Metal stamps are probably going to last forever so long as you take care of it and don't drop it. It's like any striking tool, you can bin it from being distracted.
Finally, I did grind out a simple omega symbol using stainless bar and it works pretty well. The definition isn't as good, and it's not deep enough for anything but flat surfaces (a curve will blow out the definition), but I still use it and it was free. I would reckon that most guys with any grinding experience could do the same barring lettering.
Example of pro stamp.
Hand ground stamp.