"My son was a vegetarian before he went to Morocco, and found that being a vegetarian was really difficult there. He isn't a vegetarian anymore."
"What's the polite way to survive through a meat eater's wedding?"
"I'd like to be a vegetarian, but the food's too expensive."
Don't scoff--after thirteen years of traveling as a vegetarian, I have learned the following:
1. If you're going somewhere and you're not sure there's going to be anything you can eat, either eat a bowl of cereal before you leave or take something that can be stuffed in a purse or otherwise covertly consumed. (Granola bars are the vegetarian's best friend, especially at weddings and other functions where the set menu might not have a vegetarian option.)
2. If you're traveling to another city / country, do some ground research before you go. If you're a relatively mainstream vegetarian, travel books and Zagat are good sources to consult. (Zagat recommends some surprisingly inexpensive places sometimes, although you do have to do your homework and double check prices if you're on a budget.) Of general interest travel books, I find that Rough Guide usually has the best food guide when it comes to trying to find vegetarian friendly places to eat. If your vegetarianism is more of a general lifestyle than a diet, there are vegetarian resource groups that can help you find either a good place for lunch, a vegetarian cafe in an occult bookshop, or the best vegan ashram in the state. It's all good.
3. Bagels, bagels, bagels. I'm not a huge fan of chain stores, but honestly, if I had become a vegetarian before places like Dunkin' Donuts had started serving bagels, I don't know how long I would have stayed vegetarian. Filling, tasty, cheap, good for any meal, they are probably my ideal fast food. Mmmmm...carbs.
4. This one is probably very Northeast-urban-US specific, but: pizza slices are also a (lacto)vegetarian's best chance at a quick, inexpensive lunch. An LA equivalent would probably be that corn-on-a-stick guy.
5. Delis at such enlightened chain grocery stores such as the awesome Publix (Florida and Georgia), Stop and Shop (New England), Hannaford (Maine, New Hampshire, North and Central Massachusetts),
Shaws (New England)/Albertsons (the rest of the country), Vons (California), Sainsburys (UK), and Tescos (Europe), have vegetarian options and are cheaper than their Trader Joe's/Whole Foods equivalent.
Anti Vegetarian Hall of Shame: Market Basket (Massachusetts/New Hampshire), Ralph's (California).
6. An off the cuff list of vegetarian friendly chain stores: Au Bon Pain (great pumpkin soup and spinach croissants, but expensive), Starbucks (decent vegetarian sandwich options, also kind of expensive), Caffe Nero (UK -- great ploughman's sandwiches), Pret a Manger (UK -- good selection of cold curried veggies, I've never been to the one in Chicago). Actually, I find British fast food places in general to be a good deal more vegetarian friendly than American ones, although in the five years since I've been back from the UK we've made significant strides in catching up.
7. Asian food, unless you're in the middle of the absolute boonies, is usually the best type of food to try to find if you would like to eat a big meal. Due to religious, historical, and socioeconomic issues, much of Asian cuisine is traditionally meatless. Even in places where it is relatively hard to get meat free food (Nashua, New Hampshire springs to mind), there will usually be a couple of Chinese places offering veggie fried rice or veggie lo mein.
Remember: in vegetarianism as in life, a little preparation now can save you from an empty stomach later.