Physical attraction is very important, but often one doesn't realize that the energy of the person is even more important. The energy changes the perception of the physical. Positive energy, loving yourself, self-confidence, healthy outlook on life, enjoying the company of others, healthy sense of humor, all of that project onto people around you and translate into better looks in the eyes of others.
On the other hand, friendship also changes the perception of looks. People who initially didn't impress me with their looks can impress me with their personality and heart after I've got to know them. Physical attraction do develop from that as well. We are conditioned to find people who bring fun and joy to our lives more attractive.
Not to say that physical appearance isn't something we should pay attention to. Grooming, dress, and physical fitness play a big role in attractiveness. There aren't really universal standards; your grooming, dress, and body shape should fit your personality. Just like some people are attracted to chunky guys and others attracted to slim guys, some like hairy and some like smooth, some like light complexion and some like dark, you don't have to be an athlete or fashion model to be attractive to someone.