Overt means open and done in plain sight. An overt attempt to get your teacher off-track might fail. Instead, try asking subtle questions about her kids, and she'll stay off topic all class.
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."