In most cases in males, the very first attraction is the visual attraction. I think that it's instinctive. Step 2 is to develop an personal and emotional connection. Sex and committment SHOULD come well after step 2 is cultivated.

When a sexual relationship is developed too quickly, it complicates step 2. So if you want to have a girl FRIEND, do not rush to have sexual activity. Easier said, than done.