Overt means open and done in plain sight. An overt demand for an increase in your allowance probably won't work; instead, try praising your parents' generosity and dropping hints about how high prices are these days.
If you speak French, remember that overt is the same as the French ouvert "open." If you don't speak French, give up all hope of ever learning this word. Just kidding — forgive the overt attempt at humor. English speakers, here's your trick for remembering the difference between overt and covert: overt = "open"; covert = "covered."