Here's a quick tip from a still-recovering Mr. Rewrite: Keep a list, at least in your head, of words that always warrant a second look to save you from embarrassment.
Near the top of Mr. Rewrite's list is embarrass in its various forms. Every time he writes embarrass, embarrassed, embarrassing or embarrassment. Mr. Rewrite says "R-R" under his breath. It's just too easy to forget otherwise, and people seem to want to write one R with a double-S after it (see caress, harass, etc.).
Many of those paid to know better would benefit from this technique. You'll find plenty of embarrassing errors on Google News: embaRass, embaRassed, embaRassing, embaRassment.
Another word that puts Mr. Rewrite on high alert: public. It's too easy to drop that L (spell check won't save you) and wind up with a case of pubic humiliation.