There's a ton of tutorials and stuff on youtube. Search for woodcarving, gunstocks stippling, etc. Leaving the background untreated looks kind of plain to most people, which is why stippling is traditional.
The most common type is just a bunch of dots (stipples) done with a simple punch, but there are many variations. Probably pebbling is the second most common. You can make your own tool for this, or you can buy a punch that does a few at once for a more uniform look. Leather craft suppliers sell several types of pebble punches. (you might also want to look up western belt tooling - similar technique)I've seen numerous other styles of stippling: little asterisks, scales, cross hatches, diamonds, etc.
