Everybody's different, and different things work for different people.
For some, going vegetarian 'overnight' after eating meat for many years is a very simple choice (speaking from experience). For others, a more gradual approach works better. There's no right or wrong way to go about it, the important thing is to find a way that works for YOU, and not to be too hard on yourself - otherwise what should be a very positive change can be more challenging than it needs to be (and can result in 'giving up' if it's all too 'hard'). But it's not hard, I promise
As Matt said, knowing what options are available makes a HUGE difference. I don't know when this was written, but increasingly there are more and more options available to most people in supermarkets for vegetarians that the transition is getting simpler and simpler. People can still eat what they used to -- sausages, mince, schnitzel -- without having to contribute to the suffering and death of animals.
We have a page on this site which is designed to help you 'kick the meat habit'. Here are a few tips that are on that page:
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Start with one animal, and take them out of your diet (try starting with chickens, or pigs—some of the most abused animals raised for meat). Substitute with veg alternatives such as tofu, or mock meats. Keep removing different animals until you have an entirely animal-free diet.
Pick two days a week to eat only veg meals. Increase the number of meat-free days each week over time.
Start with your favourite dish, and adjust the recipe to make it vegetarian. With many meat-free substitutes available, this should be a breeze! Work your way through your culinary repertoire until all your meals are vegetarian.
Make the switch with a friend! Not only will you have double the impact, but it’s fun and you will have someone to share recipes with.
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www.unleashed.org.au/change_the_world/go_veg/how_to_tips.php