Hi wzhu,
I wore a light beige dress suit but it looked like a skirt suit. I made sure it ended at my knees. I wore very conservative-looking black heels. The heels were < 3 inches. If you wear heels, make sure it's comfortable enough to walk in and it's not hooker-ish with those big platforms and tall heels lol. We are not there to try to look sexy and seductive lol.. we are there to be professionals. I believe heels look better than flats most of the time... assuming the heels are conservative and comfortable. I personally wore my hair half-up... just to get my hair out of my face and resist touching it. As long as your hair is neat and doesn't cover half your face, any hair style should be fine. IMO, keep it natural or simply tie it back without hair products. As for glasses or contacts, just wear what you normally wear and just be yourself as much as possible. And if you are wearing a skirt suit, make sure it's at the knees or below! Good luck!