Carry one with me at ALL times legal. On the belt (IWB) whenever clothing allows, no exceptions, no laziness.
I'm a medical student and when dressed professionally, ie. tucked shirt and tie, IWB carry is too risky. My solution to this has been in the backpack, but I am considering the ankle route. I feel this is a huge step down from IWB tactically but a good step up from a backpack stashed in a locker when I'm in a clinic.
I have also resolved to have a spare mag and light with me. Not on my person but in the pack with an OWB belt holster.
The best defensive handgun is the one you HAVE.
Best,
68W