Bring Your Squad
Having a friendly face out there makes a huge difference. My partner and I had family and friends cheering for us, and it was such a huge motivator. They also brought us water bottles and took extra layers we didn't need. Having your phone is helpful in order to find them. If they're looking at a course map and your mile times, they can also estimate what time you'll reach each mile marker and meet you there. Funny signs are a plus!
[photo via @shotsbyblake]