When you finish with meat, look at your watch and say, "Okay, no dairy until 4PM. 4PM. 4PM" (Or whatever time.) Especially helpful on short shabbos afternoons; as soon as you're done eating meat, check the clock, add the appropriate number of hours, and think about what that time will feel like.
Of course, waiting the appropriate amount of time is the halachically right thing to do, and any strategy to guide yourself that direction is appropriate. But if someone did slip up and forget and eat a yogurt an hour after their hamburger, the correct course of action is strategizing for the future, not guilt-tripping. It's at most a mistaken violation of a custom, which requires no atonement (the Nesivos says violating a rabbinic commandment by mistake requires no atonement).
Lastly, if you saw a nice yogurt and made a "shehakol", then suddenly realized oy vey! you ate a hamburger an hour ago, I've been told it's better to go ahead and take one taste (no more!) of the yogurt (assuming no other shehakol food is handy); better to violate the waiting custom than say a bracha for naught.