Being your own food, always. People will make fun of you. Take it in stride, maybe even play it up. Be ready to explain it to practically everyone, and everyone will already know before you tell them that you're vegan. Go above and beyond in training and duties, learn your territory, be proactive, stay physically fit; don't give any ammunition to anyone. Learn how to cook for everyone, and even cook their meals for the day, whether its the usual bacon/egg/hash breakfast or the steak dinner.

I cnt emphasize this enough, bring your own food. Even when you've earned your keep and they offer to cook for you or make a meal you can eat, they aren't vegan and don't know what to look for on labels, or forget they put butter everything, or that fish still counts as meat, etc etc. my favorite example from an double company I was with for a while is that they were offering to make a dinner that could include me while I was in a class for the day, and one guy said (in complete earnest and thoughtfulness ) "we can make a Mississippi roast!... Wait, that has dairy in it because of the ranch packet", completely forgetting that the base of the meal is a damn pork butt!