There are plenty of holster options out there, unfortunately, most of the good ones aren't typically what you find at the local gun and sporting goods stores. They certainly carry a variety of holsters, but for critical uses like concealed carry, the holster is an integral part of your overall weapons system.
Here is my criteria for a suitable concealed carry holster:
1. The holster must STAY OPEN when the firearm is drawn, this implies the material must be something durable like rigid leather or Kydex.
2. The MUZZLE must be protected or covered. Holsters that allow the muzzle to completely protrude, such as competition-style holsters, are not desirable for defensive use for a number of reasons.
3. It should ATTACH firmly to the belt. There are some minor exceptions that are very specific in nature but IN GENERAL, for a defensive carry holster, it should attach firmly to the belt. The belt, by the way, is also an integral part of the concealed-carry weapons system.
4. RETENTION mechanisms can be beneficial, particularly on OWB holsters. IWB holsters typically don't feature this option and it is less necessary on a good IWB holster. CAUTION - RETENTION mechanisms (if present) should not align the finger with the trigger. If you wonder why, watch this: Tex Grebner
5. The TRIGGER guard must be completely covered by the holster. No matter what you are carrying, you should carry it loaded. Since manual safeties are maybe less than optimum on defensive carry guns, you are carrying a loaded pistol that is ready to fire. The only way to keep from setting your pants on fire with it is to ensure that nothing can activate the bang switch until the gun has been deliberately drawn and presented (more or less) to a target potentially requiring a shooting solution. To ensure this, the holster must completely cover the trigger guard.
Sum these up and it creates a simple acronym: SMART
S tays open
M uzzle is protected
A ttaches firmly to belt
R etention mechanism doesn't create new hazards if present
T rigger guard is completely covered
If your holster meets these basic criteria, you are on the right track!