Many years ago, an incident in the restroom at a convenience store convinced me I needed a better concealed carry method. I had a Colt Commander tucked in my waistband when I rushed into the restroom for some pressing business. When I dropped my trousers, the Commander bounced off the floor and the patron in the next stall exited in a hurry. The next day I ordered an inside-the-waistband (IWB) holster; a Milt Sparks Summer Special.
The Summer Special has long set the standard for IWB holsters. It has several features many find desirable in a holster of this type, like a reinforced mouth that holds the holster open when the handgun is removed and rough-side-out leather that helps hold the holster in place. The Summer Special is the preferred concealed carry holster of Gunsite instructor Larry Landers.
Not everyone likes an IWB holster. Gunsite instructors John Hutchison and LaMonte Kinstel are lean and trim and find them uncomfortable. Hutchison even cautions against using IWB holsters with pistols, like the Glock, that have no safety. He's witnessed incidents where clothing bunched up in the trigger guard, causing the gun to discharge when holstered.
I often use a DeSantis Cozy Partner with a 1911 or SIG P229. It has extra leather that sort of paddles-out the edges of the holster and extends up behind the rear of the handgun. This helps with comfort when there is no shirt between the holster and your torso. The Cozy Partner is built with the rough-side of the leather against the gun. Snap straps of different lengths are available for the Cozy Partner and Summer Special to match the thickness of your belt.
Inexpensive IWB holsters made from various man-made materials are also available. Most lack a reinforced mouth and some even attach to the belt by a clip. For that matter a string can be used as an IWB holster. I've found none of these as comfortable, convenient or as secure, but they do offer the same level of concealment as expensive IWB holsters.
When it comes to IWB holsters, there seems to be two camps; those who like them and those who hate them. Comfort is usually the deciding factor, and I believe it's simply a carry method you must try before you will know for sure. Here's some advice based on what I've learned from 20 years of using IWB holsters.
Select pants with an expandable or elastic waistline, or those sized about 1-inch larger than what you normally wear.
Avoid underwear made from slick nylon fabrics. They make it difficult to keep your trousers pulled up and your holster in place.
Select cover garments that drape at least 6 inches below the waistline.
You will need to oil you handgun frequently to prevent sweat from your body from encouraging rust.
In high humidity and high heat, leather IWB holsters can become saturated with perspiration.
IWB holsters with double belt straps allow you to position the straps on both sides of a belt loop, holding the holster in place.
As with any belt-mounted holster, select a rigid, well-made belt.