If it is a girl that I'm talking to, initially her smile, eyes, facial expressions, voice, hands and body language are what I notice first. Eventually I'll get to admiring her boobs (I like them all, size does not matter to me) and then her ass...hoping for a thong being worn under her pants. I had the panty vs. thong ass viewing discussion with my husband at the gym last night. LOL
If it's a girl at a distance, I'll notice her boobs, ass, hair and her walk.