A few easy vegetarian cooking hints:
The absolute easiest veggie foods are the pre-prepared fake meats. Most regular grocery stores even have these now, so you don't need to worry about special shopping trips. I have found the best way to cook a veggie burger is in the toaster - I know it sounds weird, but they get too chewy in the microwave and you have to add oil if you cook them in a pan. Veggie burgers are the ultimate useful food if you haven't yet figured out the art of cooking tofu so it tastes good. Whatever your mom makes for dinner, you can leave the meat part out, pop a veggie burger in the toaster, and have that instead. Or if its something like spaghetti, just crumble the patty up and toss it in the sauce when you serve up your portion. Look for ways that you can make life easier by asking your mom not to mix the meat into the food while its all being cooked, then she can add the meat to everyone else's food and you can add what you're having to your part.
Also, Fantastic Foods makes a ton of great foods that come in boxes and you just add water and maybe one other thing to them to make your basic food, from sloppy joes to taco filling to a few things you mix with tofu to make it yummy. You can split the mixtures in half so you're not making way too much food for yourself, or just make the whole box and toss the extra into portioned sized containers in the freezer (old yogurt containers are perfect).
Eat lots of dark leafy green vegetables. Since you're still living at home, I'll assume you're somewhere in your teens, which means calcium is still really important for you. A lot of these dark veggies also have some proteins in them and are just all around super for you.
Tofu - learn how to cook this. The most important thing about tofu is that when you buy it in the store, its packed in water. If you don't want the little pieces that you cut it into to fall apart in the pan, or you don't want it to feel slimy in your mouth, make sure to "press" it. Pressing tofu is done by wrapping the whole block in a paper towel, placing it on top of an upside down collander, and placing a heavy plate (or two) on top of the tofu. Let it sit like this for an hour or so. Also, precooked, flavored tofus (Whitewave has some really terrific ones) are a great place to start. All you need to do with these is heat them up and toss them into your food.
The hardest part about eating veggie is eating out to dinner, at some point you will probably start to feel indignant that the only veggie food on the menu is a salad, and even those often have meat on them. The solution? Get creative. Look at the whole menu and try to find something that sounds good except for the fact that it has meat on it, then ask your server if you could get that same yummy dish, but hold the meat. Most places are pretty indulging.
Find small local health food store near you if you can. Avoid Whole Foods/Fresh Fields/Wild Oats/Whatever Other Big Chains if you can. Go to the store somewhat regularly and try to get to know the people there. They will be one of your best resources, because a lot of them are probably veggie, or at least know the products well. They'll be able to tell you if a certain product is really good or sells a lot more than a similar product.
The last tip is probably the most important one for anyone who is veggie and living in a house with those who aren't (and really a country that isn't). Remember that this is your choice. If you don't want people to question and sneer at your food choices, don't question or sneer at their food choices. Don't make a big deal if a pound of hamburger meat gets set on your box of veggie burgers in the fridge. You know that what you're doing makes sense for a lot of reasons that you have come to on your own and you know that it is the right thing to do. Its not your job to "help" other people come to these conclusions to. I have known a lot of people to struggle with this because going veggie is a moral choice and you know it to be right in your heart, but you have to know that not everyone wants to or is able to make the same big decision.
Best of luck to you in your veggie endeavors!