I deload 1 every 9 weeks or so. I try to use about 70% of the weight I was using across the board, but add in a little more volume. So if I'm DB pressing 100s for 3 sets of 12, I use 75 for 4 sets of 10. I do this with all of the exercises, but keep rest intervals under 90 seconds and try and develop my mind-muscle connection more than usual this week.
Done properly, you can get a good workout, a good pump, and not poop yourself out as much as if you'd been going heavy. I almost always come back as strong or stronger than before the deload.