Kefir

I might still make this nicer, but just to get you started:

1. DON'T USE METAL!
I'm not sure if stainless steel is fine, I haven't tried it. Just to be sure, I never let the grains touch any metal. I have a plastic filter and a plastic spoon that I use to separate the kefir drink from the grains when the drink is done.

2. My workflow
I put put the grains into a glass, add milk, and shake it a little to get any left kefir drink from the grains mixed into the milk. I then let it sit at room temperature (but not in direct sunlight) on my kitchen counter.
I also shake it softly after 12 hours, to mix everything again, to get a more creamy texture (but not so hard that I endanger the grains).
After 24 hours it's done. You'll see it gets noticeably thicker. You can try if you like the taste already or if you should leave it longer. Remember the plastic spoon! (it's surprising how little it makes a difference how many grains you have in there ... of course, if the ratio between milk and grains gets too large, it takes longer, but once it's "enough", it doesn't matter if it's "more than enough" or even "5x as much as enough". It just gets more sour, but isn't thick quicker ... just an observation)
I then shake it again just before filtering, to make it go through the filter better.
That's it. Start again from "put grains into a glass and add milk" and do it daily. I do it every morning. Every evening I shake softly.

3. Which Milk?
We use H-Milch (the long lasting milk that you find in the supermarket that is not in a fridge), because we read that all the germs have been killed that could potentially kill the grains. I've also heard of people using fresh milk. I rather play it safe, but feel free to experiment :)
Also, I've heard and read that you can use plant milk (soy, coconut, ...), but I've tried once with almond milk and didn't like the result. Please let me know if you try and it works for you :)
I've heard (and according to this source), that Kefir grains can survive on different kinds of sugar, like lactose, stahyose and sucrose. Therefore they should also be able to survive and grow in soy milk. But I haven't tried that.

4. To wash or not to wash the grains?
This is some kind of religion. Some people wash their grains every day, others every few times, like once a week, others only occasionally, and others never. In most sources I've read that when you wash it too often, it starts to get slimy. I've noticed a little slime on mine as well lately, although I don't wash it often (every few weeks or so). I assume it might be due to the fact that I just had too much grain volume compared to too little milk, but I'm not sure. Just to be sure it's not from washing, I don't wash often. Everyone must find that out for themselves.

5. When you want to take a break

• If I just want to have a break of 1-3 days, I do everything as normal, but put it in the fridge instead of at room temperature. It basically pauses during that time. I take it out early enough to be ready for when I want it again. But then I've noticed it having more a taste of yeast, which I dislike. It tastes much better without this slowing down in the fridge.
• For a little longer break, e.g. a two week vacation (I haven't tried this, but it sounds logical): Again put it in the fridge, but add a lot of milk thinned with water in a 50/50 ratio, just so the grains have enough food, but that it can't get so thick as normally Kefir does.
• For a really long break: Put the grains into a container (Tupperware or the like), add a good amount of milk (e.g. 500g) and put it in the freezer. The milk is the food for the grains while cooling down and later heating up again. When you want to stop the break, just take it out of the freezer and let it rest for a day until it's all at room temperature again. Throw the "drink" away and prepare a new Kefir just like normal. The grains should recover instantly or after one iteration. I've tried this already twice and it worked wonderfully (for approx. 2 months freezing time).

6. What to do with all that Kefir?

Obviously you can't only drink Kefir. We immediately used it as a Yoghurt replacement on our breakfast muesli. But there's more:
I like to bake my own bread as well (Sourdough ... ask me if you want some :D ) and I love cream cheese on bread! Since we have Kefir, we make our own Cream Cheese/Curd/Tvorog:

After filtering the drink from the grains, put the drink into a dishcloth, close the top tight (so no fruit flies can get in) and hang it above the sink or a bowl. Let it rest for a few hours, so the whey can drip off. The longer you let it hang there, the "dryer" the result will be. Also, the mature the Kefir drink is the more sour the result will taste, which usually you want, so we usually let the Kefir rest for more than the 24 hours when we want to make cream cheese.

When it's not dripping any more, it can be called done (unless you want it more dry, just try a few iterations to find out what you like). When it's done, just take the cloth off and scratch the cream cheese into a bowl. It's now ready for consumption or can be seasoned to your liking.

Enjoy! And if you have questions, feel free to ask! :)