I have been making my own yogurt with abandon.
I hadn't made yogurt so industriously since my 'Greek period' in the early seventies.
Then we used wooly jumpers and towels to keep the ferment going.
But today I use my 'Hot Bag' which I imported from South Africa.
My hot baggery is a domestic essential and I find many uses for the insulator -- including making my own yogurt.
If you haven't got yourself a Hot Bag yet, and you are in yogurt mode -- use a sleeping bag.
Aside from a quantity of milk and a stirring implement all you need is a cooking thermometer -- preferably one with large numbers as they can be hard to read when the lettering is minute.
But it's easy so long as you are prepared to set aside the time to stir the pot on the stovetop. A big pot makes sense.
Big pot=more yogurt.
And don't burn the milk. Keep within the temperature parameters.
Being a man I have trouble doing two things at once so pot stirring tends to be a full time project. Depending on your skills and the pot volume : 10 -20 minutes at the lactose coal face.
Then next morning after you've tucked the lactobacillus away in its cosy chamber you get yogurt.