Face your target, keep your arms uncrossed, and lean forward slightly. Keep your seductiveness subtle. Sexy is not the same as flirtatious, and an overly seductive manner or dress kills flirting. Learn to dance. At least, move to music in private.
All great flirts have music in their being.
Smile when you don't know what to say, and smile to show you're impressed with your target. It's still the most potent flirting tool.