It's going to differ with each guy. What makes my heart skip a beat may make the next guy want to wretch. Generally speaking, the 3 B's are pretty generic attention-getters. Boobs, belly and butt. If those three are in shape, you'll get attention.
Then you get to all of our personal preferences, which are a whole different can of worms. This goes for physical, as well as characteristic attributes. Some guys like a woman's hair, some guys (like me) get caught up in their eyes, others go for their attire. Some guys like the shy girl while others like the one in the limelight. There's something that'll just catch a guy's attention, and it varies from guy to guy.
What kind of guy are you looking for? Figuring that out will go a long way in answering your question more precisely.
Girls have their own tastes in guys, just like guys have their own tastes in girls. Personally, I think girls are attracted to specific looks and personalities- generally based off of how they dress/act/ etc.
I personally am attracted to girls with long hair (doesn't matter if it's curly, straight, wavy) and bangs. I also really like full lips and big green eyes. I like girls who care about their physical appearance, but don't go overboard. I like girls who don't play hard to get, but are hard to get because they respect themselves. I like girls who are friendly and approachable. I like intelligent girls who have something going for them.
And above all, I don't like clingers- they make me feel stuck, and I don't like that feeling.