Unique is key! I wear a lot of Masonic jewelry, something which most people our age are clueless. Lots of all seeing eyes, iron crosses, double headed eagles, skull & bones (memento mori), things with latin. You probably think that sounds trashy but my pieces (4 rings, 1 necklace, not all worn at once) are actually very classy and not cheap. The symbols are subtle but great for conversation once someone notices (and girls will always notice your jewelry). My favorite is inscribed with "VIRTUS JUNXIT MORS NON SEPARABIT" "That which virtue unites, death cannot seperate." Maybe its just me but girls seem to REALLY like that line.
One problem; first you need to become a Mason. Like they say, to be one ask one!
Chicks are not the reason I got into Freemasonry. I just found when girls see Masonic jewelry they immediately think you're some kind of bad boy hell bent on world domination (which has nothing to do with Freemasonry).To come full circle, find pieces that are unique to your pesonality. That way when you're asked, "why are you wearing that," you can tell the girl something about yourself and not "I think it looks really cool!"