What Seaside said.
I get hit on by young men a lot up until about 1.5 months ago when I began to "show" in my clothes. Let me tell you, you've already screwed up if the words "cougar" or "MILF" ever cross your lips. It's NOT A COMPLIMENT. Also, anything along the lines of, "You're attractive for an older lady," will also get you disgusted looks. If you want to say that she's hot, just say that she's hot. Don't qualify it by saying that she happens to be hot for an older woman. Emphasizing her age or your age difference will not impress or seduce.
Really, just flirt with her like she's another other woman.
I agree. MILF, cougar, "you look good for your age" don't work with me. Then again, some guys could totally get away with saying it (those charmers! lol) I do prefer younger men - maybe not young enough to be my kid, but I tend to have more in common with guys younger than I.
And us "older" women like to be treated like women. Inside we don't feel "old". We still like to be admired, flirted with and desired. Be interested and be interesting.