Lake I have a bag of 'em. Blessed BIG BAG of holsters.
Here is what I've found the hard way.
Slip on holsters slip.. around. Hard to get a good one.
IWB holsters work if your waist line does not vary to much (and get the pants 2 inches larger in the waist to compensate for the gun.) Best place for the IWB is the appendix carry position if it's a snub. Works very well with me. Even a Glock 27 conceals if you wear a baggy T-shirt. Longer barrels don't work as the gun ends up poking a very tender part of ones anatomy.
Belt slides do work and are very convenient if you have a coat, wind breaker, or sleeveless jacket. Do skip the photovest or fishing vest stuff. It looks stupid and shouts 'gun'. I also find barrels longer that 4 inches poke into the seats of the car so a good 3 inch .357 or .38 works real well. Glocik 27 works well there to!
Ankle holsters work if the gun is very light. TCP/LCP/P3AT do work well. Glock 27s don't unless you like having a brick tied to your ankle. And yes I have a Apache holster for my TCP!
Thunderwear/hotjocks do work if you put a TCP/LCP/P3AT or even NAA .22 revolver (I have the NAA PUG .22 magnum BTW.) Use the Thunderwear stuff with jogging cloths. Regular blue jeans don't work so well as it makes you look like you are a potato smuggler.
Shoulder holsters feel like bras and I DON'T WEAR A BRA. OK?
Pocket holsters do work well with, again, TCP/LCP/P3AT/NAA .22 or airweight snub. Anything heavier the coat swings around like a pendulum.
Fanny packs can work if wherever you are fanny packs are common. Here in Texas they are NOT!
So basically I find myself with a IWB and belt slide for my guns. I can go from a Glock 27/26/33 to a Ruger GP-100 3 inch .357 to a S&W 640 .38 (my first carry gun.. still have it to!) I use the ankle rig very rarely.
Hope that helps.
“We can evade reality, but we cannot evade the consequences of evading reality” Ayn Rand