What do guys notice first about a girl?

Naturally different men will look at different things, it depends on the man, but there are also some pretty standard things that men look at:

The first things a man will pick up on when he meets a woman are rather unpredictable, but men usually look for something of themselves in her. Just like when anyone meets anyone, they are intrigued in similarities. That means that a man will probably look for his best qualities in a woman (a smart guy will look at smart women, and a funny guy will be impressed with funny women, etc.).

The issue with this immediate response is that it doesn't correspond with our long-term desires. Having too much in common with someone is just as annoying in the long-term (especially romantic relationships) as having nothing in common.