Being vegetarian in 2013 is much easier than it was in 1993, which is the year I turned 16 and ate my last meat. (It was corned beef hash from a can! I can't tell you why but I loved that stuff.) There are now Internet resources, many more restaurant options (I was thrilled if I could order a veggie burger in the mid-'90s) and generally, people are much more understanding of what it means. Because we have seen so much media concerning the health and environmental issues associated with regular meat-eating, plenty of omnivores go for days being a temporary vegetarian or prepare veggie meals to reduce cholesterol, cut their CO2 emissions, or because they are on a budget. And with so many people eschewing gluten, dairy, meat or one or another allergen, society in general has become more accepting of a variety of dietary issues. That being said, vegetarianism still isn't totally mainstream, and is much more challenging in some places than others. (In my opinion, France and Spain, the American South and Midwest are all horrible places to be veg, while Italy and England, California, Hawaii, New England and New York have lots to offer.) Here's what I've learned over the years that works for me.
Educate yourself: This advice goes for literally every human being on Earth. Most of us aren't taught much about nutrition growing up—my family is and was extremely health-conscious, but even with all the dinner-table conversations we had, I never received an in-depth nutrition education until I went after it myself in college and afterwards. Most people living in developed nations who eat a 'standard' diet are missing nutrients, overindulging in sugars and processed fats, and not eating enough veggies. So whatever your food choices, get some knowledge about what to eat, but if you are going vegetarian, or even thinking about it, do some serious reading (see below). There is no need for supplementation in a vegetarian diet, and yes, you can get all the nutrients you need from your food, but it's likely that you probably have some holes, nutritionally, since most of us do. For some people, converting to a vegetarian diet when they are already (unknowingly) under-nourished can make them feel awful. And for most people, vegetarianism actually makes them feel much better, lighter, healthier. That's what you are aiming for.
Listen, read or watch some experts: There are a plethora of books, documentaries, podcasts and other media that are free or very low cost to access. By exposing yourself to a variety of personalities and media about the topic, you will be able to figure out what works best for you. Some great resources include the Physician's Committee for Responsible Medicine's Vegetarian Starter Kit (which includes great info on a number of topics, including for pregnant women and parents of vegetarian kids). Skinny Bitch is an in-your-face (and funny!) guide to going vegan, Herbavoricious (website and a book) has many inspiring recipes, plenty of them pretty fancy, so you can impress your friends. I also love Alicia Silverstone's book and site, The Kind Diet. Forks Over Knives is a great doc that is both inspiring and informative in how to eat a whole-foods, plant-based diet. Food, Inc. and Fast Food Nation are two additional easy-to-find films that do a great job of documenting and exposing where our food comes from.
Learn to love vegetables: The fundamental key to being successful and long-lasting vegetarian is to figure out how to eat a lot plant foods. Many wannabe veggies start out by just cutting the meat from their diets, which ends up meaning way too many grilled cheese sandwiches and pasta-and-sauce meals. After a time, this will make anyone feel crummy, not to mention make you feel bored and deprived. Embracing the huge variety of delicious vegetables in the world will not only keep your palate happy and amused, it will lead to long-term health gains including healthier, glowier skin, a lower risk of cancer and heart disease, and better digestive function. If you think you don't like vegetables, you haven't done enough exploring of the incredible variety of ways they can be prepared and enjoyed. Many people have just never experienced fresh, flavorful veggies cooked (or uncooked) properly.
Flexibility helps: Every once in awhile, I end up eating soup made with chicken broth, or knowingly finish a friend's mashed potatoes that has meat-flavored gravy on it. After about 10 years of vegetarianism, I loosened up and realized that throwing away a whole sandwich that had a piece of bacon on it by accident (I give the bacon to a friend or my dog), or tossing a cup of soup made with chicken stock after I had already paid for it was silly and wasteful. What matters in life is what you do 99% of the time. I'm not a perfect vegetarian, and I don't try to be. When I'm at a restaurant that has locally-caught sustainable scallops, or oysters, or an event where they're being served, I'll sometimes eat them. I have no ethical problem with eating crustaceans and bivalves (though they do have a heavy environmental toll when harvested non-consciously), and it's not often that I come across those that meet my standards (or can afford them), which means it happens infrequently. It's one of the reasons that my vegetarianism the other 99% of the time survives; it's never an all-or-nothing, I-won't-let-the-chicken-broth-touch-my-lips proposition. Over the past 20 years, I've not eaten about 600 land animals, and about 4,500 fish (that's a conservative estimate based on the excellent calculations here). And you know what? That's good enough for me. I think the best way of making any commitment last is to be a little flexible about its implementation. I'm sure not all vegetarians will agree with me here, but that's how I've made it work for me.
Don't let the meat-eaters bully you: Over the years I have been bullied, cajoled, shamed, made fun of, and pissed off plenty of people who eat meat. I'm not sure why what I put in my mouth (or don't) has such an effect on other people, but expect most people in your life to have an opinion on if you go vegetarian or vegan. For some reason, it makes some people very angry. This is totally normal (in that it's common and I've seen all sorts of people engage in it), even among otherwise educated and enlightened people. You can go decades, or your whole life—just ask all the Indian Hindus who haven't eaten meat for generations about it, or Seventh Day Adventists, who have been veg for 130 years— maintain a healthy pregnancy, breastfeed, and raise children vegetarian. The health effects of a vegetarian diet are overwhelmingly positive, for both personal health and that of the planet. I argued with a lot of people when I first became veggie (and it's easy to do when you are first learning and excited about something new in your life) but after awhile I saw that most of the time, it just made them angrier. So then I started asking them why they cared so much about what I put in my body, and that generally shut them up. Don't try to tell people what to eat, though it may be tempting when you start learning how awful most mainstream meat is, but do stand firm in your choice and become a resource to those who might be interested in hopping on the ever-growing meat-free bandwagon.
Don't forget to enjoy your food and eating it no matter what your diet, and good luck.