Remember to ask for it when you reserve your ticket, and then call with a reminder again 24 hours before departure. Tuck a piece of fruit and some crackers into your carry-on luggage in case your meal doesn't make it to the plane. It may be simplest to pack a small cooler with fruits and juices, cut-up vegetables, yogurt and sandwich spreads. Also, take non-perishables such as peanut butter, crackers, nuts and dried fruits for lunches. Check in the phone book for vegetarian restaurants, or call a local vegetarian group or natural foods store for restaurant suggestions.
Many vegetarians let their host or hostess know about their eating habits ahead of time.
I'm quite happy eating the breads, salads and vegetables you prepare. Here's one sample menu for a vegetarian Thanksgiving feast. Selected items from the list can be found in Simply Vegan by Debra Wasserman.