Well, first of all, don't get frightened and don't panic. When I first switched to vegetarian diet, it was as simple as ordering cheese pizza instead of the average pizza (I eat out a lot and am the worse cook in the world). What I want to say is, I didn't have anything planned at all. I just knew I didn't want to be a part of the meat industry anymore.
In the first week, I was constantly tired and ran out of energy very fast; the side effects of lacking iron. Don't worry - there are plenty of ways for you to get iron as a vegetarian (like eating parsley), I just wasn't really paying much attention to what I ate. I also lost five kilo's in the first week, mainly due to not consuming any fat (you can get healthy, plant based fat from soy stuff such as soy omlettes and soy pudding).
I just want to tell you that, even if you don't plan anything at all (which was my case), you can't get -too- wrong. You get the hang of it eventually, as your body will naturally tell you if you lack something (you will feel different). But once you figure it out, you'll feel fantastic, and you will never feel the need for meat again. Take my word - I was the greatest fan of steaks in the world before I turned vegetarian.
I see you've already been provided with a few links, lemme just throw in my own ---> www.GoVeg.org
I'm sure you'll find some useful information there, as well as some other reasons (apart from health) why you should go veg. And also note that, should you really be concerned about nutrients, you can always visit your doctor and have a talk with them.