Last school year when I took physical science, I had forgotten to study a particular question that popped up on my review the day before the final exam dealing with double displacement reactions in chemical equations. It was three things that must form for a double displacement reaction to take place. These things were:

To remember it I came up with this obscene nmemonic:

Paul wants Gabby (to) fuck Doris Day standing for Precipitate, Water, Gas forms --Double Displacement. At this point, it would probably have been a lot easier to just remember those three things and get it over with. I kept forgetting the mnemonic too while I was at it. Sad.