Since there was a question about what to eat when you don't eat meat...
First you look at what meat provides. Apart from filling your belly or tasting a certain way, it provides amino acids that you need for protein, and iron, and fat, that's the main thing. Now if it's fish it's got some oils as well.
For the protein, go for pulses/legumes. That is, lentils, beans and peas. You can also have eggs if you eat them, they're complete protein, just like quinoa, and unlike pulses or meat. Lentils are high in iron, too.
Then, if you ate a completely balanced meal when you ate meat, that's pretty much the only change you need. But a lot of people, when they look at their diet, realise they weren't eating right back then either, or not filling their specific needs. At this point, you need to get some specialised advice to check if you have deficiencies or eat too much of something. Which really is the case of most people, regardless of diet.
What is generally recommended if you want a blanket advice for vegetarians, is to combine pulses and grains. As I said, pulses include peas (except green peas. So split peas, chickpeas, peanuts), beans (including, most famously, soy, but far from restricted to it) and lentils. Grains include wheat, barley, corn, rice, etc, and of course whatever is made from them (such as bread or pasta).
Then for the other half of your plate, have vegetables. Doesn't matter if it's considered a fruit (like tomatoes or cucumbers are, for instance), if it's generally considered a vegetable, count it as one.
My ex-inlaws would always have at least 2 different vegetables in a meal, and when I grew up we always had vegetables as a first dish (for instance tomatoes and cucumber with some vinaigrette, or leek, or half an avocado, or shredded carrots), then the main dish which had its own vegetable, then a salad.
But living alone, I find it hard to cook enough vegetables, so if you have a freezer buy frozen mixes or something. I don't have one so what I do is buy endives or cucumber or celery or tomatoes, and just eat them on their own, like you would an apple.
When I'm lazy, for a vegetarian meal I take a can of couscous vegetables, I put it in a bowl with some semolina and I microwave it. And then you have couscous, it has the chickpeas, the semolina and the veggies, it's simple and fast.
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