Complimenting people on their outfits is a great one. I do this a lot (the folks in my town are great dressers, what can I say?) and while about half just say thank you and move on (perfectly fine), I have had some people follow up with some other comment, like where they got it from. The last compliment I gave was to a woman with a cute skirt and she was like, “Thanks! I keep looking for the pockets.”