I hear this debate/argument every other day at my work (I work at an organic grocery market). So here goes:

If you want to go vegetarian for the sake of the animals live, sure, do it. Because at this point there is no arguing with you. You've made up your mind that eating animals is wrong, and that I can not argue with. However, I do disagree.

If you want to go vegetarian for the sake of the quality of the animals lives, you don't have to. In fact removing yourself from the pool of meat eaters altogether is not going to affect the factory farm industry very much. There are many other ways to try and change (or abolish if you want go there) factory farming without cutting meat out of your diet completely.

If you want to go vegetarian for the sake of your health, do it, but be careful. The modern vegetarian diet is filled with "meatless meat" which are essentially processed vegetarian junk foods. This isn't good for you at all (no processed foods are). If you decide to go further and become vegan, be careful. Make sure you are getting all of your essential nutrients in some form or another. Humans have lived on an omnivorous diet for a very long time because meat and dairy are good sources of essential nutrients. Unfortunately in today's modern diet, we over consume meat and dairy which does drive many to people to cut it out completely, also cutting out those essential nutrients. Being a vegetarian can potentially be really good for your health, but it is easy to mess up and screw up your body. So do it right.

I would also like to add here a point that opium, who is a raw vegan and a blogger I know from livejournal, made:

You will realize that each step makes the last seem so damn easy. Vegetarian is SO EASY it is ridiculous, but still full of nasty things that are bad for you and totally unethical. It's a "step" in my opinion. Vegan is easy to me because I am raw, and even that is easy to me because I am low-fat, so less and less options, it's a very simple diet. I do it for my health and also ethics.

I had never occured to me that vegetarianism is a "step"; a good starting place for anyone interested in changing their diets for health, ethics, or whatever reasons. She recommended I read Becoming Vegetarian by Vesanto Melina. So thanks, I learned something today!

My advice? Go organic and take quality supplements instead (Poor quality supplements will help you just as much as taking nothing. Also, aside, be careful taking supplements altogether because too much or too little of something you really do or do not need can be harmful. Everyone has their own recipe. Pay attention to your body and if you are having reactions, stop. As a good rule of thumb, if you don't think you need it, you probably don't.). Eat more veggies, less meat. But whatever it is, do it organic, and source your food. Know where it comes from and always choose humanely raised antibiotic and hormone free meats and dairies. If you have the option, ask your grocer about the product. How much do they know about what they are selling you? Farmers markets is the best, because you can ask the farmer directly.

If you don't have access to this, think "I'll have a salad with a few grains and a little meat on the side", not "I'll have a steak, a piece of bread with butter, and a side of one lone vegetable, maybe add potatoes." The biggest thing lacking in most of our diets are vegetables, but that doesn't mean you have to go full vegetarian.

I admit though, it's hard to eat healthy! I have been, as a youngster, taught that I could eat what ever I wanted (within reason, no ice cream for dinner, ect.) and have been programmed to do so. Taco bell and Chinese food were taught as "treats" and highly sought after in my family. I struggle daily to try and eat healthy and the Chinese take out sometimes wins. I do have access to some amazing resources. I get a 30% discount on all products at my work which carries only organic and natural products. There are farmers markets in my town on Tuesdays, Thursdays, Saturdays, and Sundays all of which are easily accessible by bus. I also live in a house (my boyfriend and I) which is open to going organic and eating healthy and encourages me to do so. But it's still really hard. So don't feel badly if you're having a tough time making changes in your diet. It's hard for everyone! If you do find yourself in the McDonald's drive through, don't beat yourself up over it. Just try again at the next meal.

These are two fantastic book which may help influence those considering making a switch in their diet. In Defense of Food by Michael Pollen & The Organic Manifesto by Maria Rodale.