There's not much to it, just don't treat Tofu as replacement-Steak. The key, to me, is that instead of "main dish and side dish" style of cooking (IE, a steak with a side of rice and veggies) I do "single, rich dish" cooking - for example, rice with a carrot and sweetpotatoe Daal, or a stir-fry.
I try to have at least one warm meal a day, and usually a bread-eggs-and-cheese either as breakfast or as a light dinner if lunch was heavy. As a vegetarian, eggs become a major source of protein - I usually have at least one a day, often two, with my bread. Cheeses and milk-products feature heavily. Legumes are also a great source of protein and become a major part in many dinners, as part of the sauce. Asian cuisine is a good source of inspiration - I do a lot of Indian and Thai, for example - or "Farmer's Stews" ("Whatever you've got in the fridge"-stews) that include some kind of bean, root vegetables and usually greens.
I know not every country has good, affordable fresh produce - but if you do, it shouldn't be any problem to follow a vegetarian diet.
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