I just lay them out on the paper and put a sheet of glass over them to press them flat (glass from an 8x10 or 11x14 picture frame). Set enlarger to project well beyond the area you need to cover (so there is little light fall-off). Use grade 2 filter if you have.
Find the minimum time for each film type to just get to maximum black through the film rebate (edges) for a mid-aperture exposure via test strip. Record aperture, time, enlarger height, and contrast filter. Use these settings each time, so you don't have to go through the test strip thing each time. If you standardize like this, then a quick examination of the contact will give you hints about how to make your projection print.
I usually try to make contacts as soon as the film is dry, but before I sleeve them -- when I'm organized.
(If contact prints are too dark, consider increasing your in-camera exposure. If prints are too light, consider decreasing your in-camera exposure.)