It really depends for me; time of day, year, or mood.
However, one thing is usually consistant...bead head flashback PT.
If that's not working, a variation of PT usually stings a few fish.
Of course, I can't complain about my more "hatch specific" imitations. (At work, so I can't show pictures) However, I study pictures of the real thing and mimic it the best I can.