In a large pot, bring to simmer a litre of milk. There is a specific temperature that it should reach, but I do not own a thermometer. I just let it get to the point of rapid simmering, without breaking into a boil. At that point, add 2-3 tablespoons of vinegar. This will cut the milk and separate the whey from the curds. The curds will be your cheese.
As soon as you add the vinegar, turn off the heat and let it sit for a few minutes. The process happens quickly, but give a good 5-10 minutes.
I like using coffee filters to catch my curds.You can use a cheesecloth if you have it. Simply place a filter in a mug or bowl. Then gently scoop out the curds with a slotted spoon. Plop it in and let it sit as the watery whey drains out. Give it a bit of a squeeze to help it along.
When you are done, you will have a something that looks exactly like ricotta cheese. Add a bit of salt, and it will also taste exactly like ricotta cheese!
In no time you'll get creative adding seasonings and herbs to create your own flavored cheeses!