The easiest way to go is to work out a menu for the week. Have a whole list of what you're going to eat at breakfast, lunch and dinner. Since you're living at home, it is a little harder, so i'll try to help you out. (If you're going vegan, tell me. I will customise a list fo vegan ideas instead of vegetarian ideas

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Breakfast:
>All different types of cereals - Coco pops, corn flakes, weet bix, frosties, fruit loops.
>Toast with vegemite or peanut butter
>Baked beans/canned spaghetti
Lunch:
>Vegemite or Peanut Butter or Jam Sandwhiches
>Also, if you go to the super market you can find all sorts of quick meals; 2 minute curry meals, noodles and heaps of frozen food.
Salads - so many different kinds.
Dinner:
>Pasta - If you're family is having pasta for dinner, just ask if you can have your pasta, sauce and cheese before you're Mum adds the meat.
>Sausages and mash - If you go to the supermarket, you can find vegetarian sausages from Sanitarium. Just swap these in for the meat sausages - I'm sure your family won't mind.
>Soups and bread - All sorts of different kinds of vegetarian soups.
>Vegetarian pizza
>If you're having tacos, just swap canned mexican beans in for meat.
>Roast- If you're having roast, maybe on Sunday night or something, you can have mock-roast. Again, look under the Sanitarium section in the refrigirated section for the fake roast. Then just have that with everything else; potatoes, carrots etc.
>Subway veggie patty
>Hot chips
>Vegetarian sushi
There are SO many different things - just google for ideas. For example: "Vegetarian meal ideas."
Dessert:
>All sorts of things lol - ice cream, apple pie, etc etc
P.S -
It might be a good idea this weekend to talk to your family about your decision to go vegetarian. Show them this menu and let them know your serious and this is a mature decision not a 5 minute fad. If your parents want to know why, ask them to go to AnimalsAustralia.org.au or Meat.org
Ask your parents to sit down with you. Have a 7 night menu on hand to show them you're HEALTHY ideas for the week - emphasise it is a healthy diet.
You have to make sure your parents know the reason why you want this.
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Always remember everyone on this site is behind you! After a few months your parents will know you are serious and will accept your decision. In fact, I'm sure they will help you out with it!!
You can go to VNV.org.au for more help.