First off, as one of my PC stat sheets, i have a "compares to spot" column for the various skills the PC has that i might need him to roll. like say spellcraft. For example, if his spot is a net +7 and his wilderness lore is a net +4, the compares to spot column for Wl is "-3." I include saves in this column as well. This is handy for things like sense motive and bluff as well.
This way, whenever i want a secret die roll, i just ask for a spot check and adjust what they report to me to give me the correct info.
I tend to ask frequently for spot checks, especially on entering the room, to gauge how much info i give "at first glance." As such, my players are not usually that jumpy when i ask for spot checks.