I'm currently on week three of my half-marathon training schedule for the FITNESS Half-Marathon, and my feet are starting to look very callused and all-around rough. Heidi Waldorf, M.D., a dermatologist in New York City, recently gave me this cool tip: Before you put on your gym socks, slather on Vaseline all over your feet. "Vaseline will help soften your skin and also keep you from getting a blister," Dr. Waldorf says. If you have calluses, Dr. Waldorf suggests using a lotion or serum with salicylic acid before Vaseline. Post-treadmill you'll have baby-soft feet.