If you want to attract her attention, do normal decent-human stuff like making eye contact and smiling in a non-threatening way. If you do want to approach her, play it polite and open. Don't crowd or leer, and don't make obvious references to her age or body. Keep your introduction short and sweet. Let her know she caught your eye. Tell her you're interested in getting to know her. Offer to buy her a drink.
SIMPLE. If she's interested, she'll reciprocate in her own way.
Be upfront about your expectations
Vague intentions, game-playing, and a lack of communication are just some of the crappy dating behaviors younger ladies have come to expect. Offer her a welcome departure from all that crap by being self-assured, and straightforward about your intentions.
Be honest with her: would you like a simple date? Something more? Are you genuinely interested in pursuing a relationship? Let her know, and see what she says. Older men knowing what they want is hot.
Address the wizened elephant in the room
Don't assume every woman you pursue is A-OK with the age gap. Ask how she feels so you can anticipate possible conflicts down the road. She may be new to dating older men, have her own personal reservations, or not even be aware of how old you are. (In which case, keep doing what you're doing, it's totally working.)