I've been making my own yoghurt for well over a year now. I've been doing it by boiling milk, then letting it cool, mixing with live yoghurt and milk powder and then wrapping it in a warm towel and leaving it in the airing cupboard next to the hot water tank for 10 hours.
Now we've got a yoghurt maker! My mom had one when we were younger and as I recall it didn't make very thick yoghurt. (The yoghurt I've been making up to now has been really thick and creamy and silky.) So I wasn't all that convinced this was going to work.
I learnt that you should use UHT milk, which I didn't know stands for Ultra Heat Treated milk and is the long life milk. It worked perfectly! I didn't even add the milk powder I usually do to make it extra creamy. I always add a bit of vanilla though which makes it taste really good.
The yoghurt maker takes 7 pots and it took 1 liter of milk to fill with 2 teaspoons yoghurt per pot. Each pot is a perfect portion size for breakfast. Plug it in and leave for 9 hours. It also comes with an extra 7 pots so I don't have to wait for the first batch to be emptied before making the next lot. This way we can always have yoghurt. And reserve the last pot to make your next batch.