One thing I have started doing fairly recently is to tone and dry (completely) my test prints. I've found that without a dried, toned, correct print, it is impossible to tell how much darker things will end up. I know this is pretty basic, but it took a while to see how much variation there is on a proof sheet or print.

I'm using Selenium rapid toner in 1:9 dilution for 5:00 on Ilford's RC paper. No purple, just rich, deep blacks.