Great EDC gear is awesome, but if it's a pain in the butt (or hip, or appendix) to carry, the will so suffer the discomfort can be a major detriment to actual EDC.
Pocket clips seem to be the most popular way to keep an EDC light handy, but I personally protest them mightily (YMMV).
I generally prefer to just drop a light in my pocket, but that is not the perfect solution either - though an inside pocket holster helps this method considerably.
Lamenting the fact that there may be no one perfect method, I have for years experimented with carrying my fight light in a belt carrier. Vertical carry I find uncomfortable, but horizontal works well for me. The following photos depict my latest (and perhaps greatest results) experiment;
From left to right: (1) a horizontal carrier I made from a vertical holster; (2) one of my favorite EDC fight lights and (3) a 2-inch elastic belt keeper.
Light inserted in carrier. Tension is adjusted to provide a reasonable level of retention while allowing easy extraction of the light.
Elastic belt keeper placed over tailcap greatly enhances retention.
I wear this setup weak side at the nine O'clock position. It's undetectable from both a concealment and comfort standpoint.
In use, I pull the keeper rearward to disengage it from the light and then pull the light. Placing the keeper over the tailcap is easy - I place my thumb under the rear edge of the keeper and pull it up and over the tailcap.
The carrier pictured is no longer available but looks straight forward to make for this configuration. I would eliminate the cover on the bottom and simply crimp the bottom of the carrier to prevent the light from falling out. A split loop attachment works perfectly and allows simple construction of the carrier itself for both 1-inch and 1.25" diameter head lights.
To take this further I guess I'll need to learn how to work with Kydex and make a few carriers for others to try.