what mountain you climbing? I was just in the whites about a month or two ago.
pretty much like everyone else said, stay away from cotton cloths. the whites are notorious for unexpected weather. it may be sunny and warm at the summit, and an hour later be cold and rainy. rain jacket is a must, along with some kind of synthetic pants, shirts, ect. good lightweight hiking boots are preferable, but based on the length of your hike, anything should really do. i'd carry at least two liters of water with you to stay hydrated.'
for snacks, snickers are the bomb of top of a peak.
bring a camera too, the views are going to be incredible this time a year, with all the leaves changing colors.