I have often worn an ankle holster. For what it is worth:
They are terrible places for a primary gun. They are slow to draw from except while seated, and you aren't going to do it while running. A heavy gun on your leg isn't going to be very comfortable for long, and I have heard of people developing leg problems from wearing too heavy a gun for too long on their ankle.
They are an excellent place for a small, lightweight backup gun. They are accessible when a primary gun elsewhere might not be accessible, such as when wrestling on the ground or seated in a car. The smaller, lighter weight guns cause less discomfort, and you can almost forget you are wearing a lightweight gun in a well-designed ankle holster.
Unless you wear boot-cut jeans, forget about ankle carry while wearing jeans. The holster will be difficult to access and will create a highly visible bulge. Stick to dress slacks. Make sure the leg is long enough and the fit around the waist and thighs is loose enough so that the holster stays covered when your pants ride up from sitting down.
Forget about ankle holsters with leg garters. They are very uncomfortable, and if you use the garter to increase the height of the holster, it will ride down and start rotating around your leg. It will also print more. Instead, get a holster without a leg garter, wrap it around the smallest diameter part of your ankle, and buy your pants appropriately for this mode of carry. Your holster will stay put quite well.
Padding between the gun and your leg is an absolute must. I prefer a thin layer of felt that extends beyond the edges of the leather ankle band. Sheeps wool works with synthetic ankle bands but will allow the edges of a leather band to cut into your ankle. Avoid big felt pillows under the gun that don't extend beyond the leather.
I used to wear ankle holsters under my sock to improve concealment, but gave up doing so. The sock adds to the cushioning if it is under the holster, significantly improving comfort. If your pants leg rides up, the sock may hide the holster, but the bulge in your sock will be so large that it will make little difference. Again, buy your pants to accommodate the holster.
To draw while standing, take a big step back with the right leg (assuming the gun inside your left ankle). Lift up our pants leg, bend at the waist, and draw.
I can take or leave retention straps on ankle holsters, as long as the holster is molded to the gun to provide some friction retention, and as long as the retention strap has a thumb break and is otherwise permanently attached to the rest of the holster. Straps that secure with velcro, or straps that simply extend over the gun and snap to the holster body, can come undone if bumped while you walk, permitting the gun to potentially fall out of the holster. I will trust an open-top, well-molded ankle holster to hold my gun more than I will trust a universal holster with a retention strap.
Hope that helps.
