(From the pickups i have next to me right now)
Covered Pickups: On pickups with a cover (nickel etc), turn them over and look at the little screw heads underneath because sometimes they have wax in them or sometimes theres a lot of wax on the underneath.
If its open coil (zebra etc): this is a bit harder in my opinion, but look at the top of the pickup (the coloured bit), and notice there are 4 small holes (slightly bigger than a full stop size), these can sometimes get filled with wax (not always), or sometimes on the top there might be a bit of wax on the coloured bit, but you have to look carfully!
hope it helps.
carlsuth