everything here seems like super advice! I did one of the ms150's last fall, where our first day was 90 miles. Not quite a century, but fairly close-- and a friend gave me the most helpfull 2 bits of advice I got before the ride: make sure and hydrate for at least a day or two ahead of time (although I see that one was already mentioned) and while you're riding, move your hands and kind of swing your head from side to side every so often to prevent your arms/hands and neck from stiffening up. Looks goofy, but at mile 75 I appreciated it. Good luck! you can do it