Ex or current Jailers/Corrections interdiction within a facility

So eventually I want to go on the road and focus on interdiction type work. What are good things to do besides randomly searching cells within a facility to kind of start getting in the groove of this? What signs or clues do you guys look for in housing that suspects someone may have some drugs stashed away? I want to be able to “randomly” search a cell where I have the best chance of finding some dangerous contraband (and I don’t mean extra towels or any of that bs)