If you're using a PCB most build documents include a drilling template. Usually its a PDF so just make sure you print it out at 100% (as opposed to "scaled to fit page"). Of course you still want to double check everything before drilling; make sure the template PCB is the same size as the actual, that the pots/switches line up, the PCB fits into the box (sometimes the screw holes in the corners require you to mount the board a bit lower). If its your first time drilling an enclosure out I'd suggest using a cheap box as a test. Have fun and welcome to the community.