I never have trouble spelling 'desert' and 'dessert' correctly because of my fifth grade teacher, Mrs. Bell.
She one said to me, "Which one would you rather have two of? A big, sandy desert or a delicious chocolate dessert? You would rather have two ice creams than two dry deserts, right? Then you put two s's in dessert and just one s in desert."
And I've never misspelled it since. However, I still have to think back to Mrs. Bell's memory trick to get it right, lo these twenty years later.