It is best to clean off the skin first with a little alcohol.
Any lotions or soap residue will affect adhesion negatively.

Also, since Lidoderms use a water based aqueous adhesive any moisture/sweating will dissolve them and then they move around.

I put them on the tops of my feet (not the bottom) and interrupt the nerves
before they get to the ankle. I have found over the years that putting them
on the target pain, is not as useful. If you are trying them on the bottom of
the feet, there are many sweat glands there, and that may be your problem.

The only place I have problems is in the lower back. Especially in the summer.
I use a plastic micropore tape by 3M to keep them in place there. They typically stay on the backs of my knees and top of the foot with no problems.

Placed where there is friction or moisture/sweating and they absorb it like a sponge. Once I took one off on the dock up North on vacation, and forgot it there, and it swelled up like some alien thingey! Weird.