Making yogurt is so very easy and you probably have everything you need already.
Put a wooden cutting board on the counter and lay a heating pad over it and set it to medium.
Pour a 1/2 gallon of milk into a pot and heat to 185 degrees. This kills any 'bad' bacteria and sets up the milk to accept the good bacteria. You can use whatever fat percent you want but I love whole milk for mine. While it's heating put some cold water with ice into the sink to a 6 inch depth. Once the milk reaches 185 put the pot into the sink (be careful not to slosh water into the milk). Cool to 110 degrees. This is the perfect temperature for the 'good' bacteria in yogurt to multiply.
Remove the pot from the sink and empty a container of plain yogurt into the milk. You want to read the label and make sure it contains "Active cultures". You only really need a few tablespoons but I just dump the whole thing in the milk minus the few bites I take
Stir it until it's all dissolved and smooth. Put the entire pot on the heating pad and cover with a lid then wrap the whole thing in towels. Cover it all up and leave it alone for 7 hours.
Unwrap it and stir it up a bit. Now you can pour it into old ricotta or sour cream containers.
An easier alternative is a 'yogurt maker'. I have one. It comes with small jars that you pour the milk/yogurt mixture into and then cover it with the lid and plug it in. It creates the heat of the heating pad for you. Plus you get the nifty little jars
to eat the yogurt out of.
If you want a Greek yogurt consistency you can line a bowl with a clean dishtowel. Now pour the FINISHED yogurt into the tea towel and gather up the ends of the towel. Hang it from the sink spout and let the liquid drain into the bowl for an hour or so then spoon the drained yogurt into containers. Be sure to save that liquid. It's AMAZING in bread recipes.