Physically, someone who takes care of herself, preferably with long hair and anywhere between the regions of 5'3" (160 cm) to 6'0" (183 cm). Not stick-thin but not the opposite either, somewhere in between would be best. Hate it when they're caked in 16 layers of makeup and fake tan 24/7, basically looking like they escaped from Area 51 after a freak nuclear accident.
Personality-wise, someone who is pretty laid-back, intelligent, knows how to have a good time but isn't overly-boastful or narcissistic. Would be a huge bonus if they were into nerd-type stuff. Ultimately, someone who would just be herself and not try to put on a kind of facade or try to be someone she isn't. After all, we guys can see it from a mile away.