These steps will work for rendering any kind of renderable fat: lard, tallow (beef, goat, sheep, and wild game), and any kind of fowl: geese, turkey, chicken, and duck.
1. Get skin of animal whose fat you want to render.
2. Get a large pot, one with a lid is best. If you don't have a lid, pretend you're from Idaho and use an inverted plate in its place.
3. Put the skin in the pot, and put the lid, or plate on.
4. Turn your burner on medium low.
5. In 1 - 1 1/2 hour(s) turn the heat to low. (Optional)
6. Let the skins cook on this low heat for a few hours, stirring every one or two hours. (The smaller the amount of skins you are cooking, the less amount of time you will need to cook them for.) You'll know it's done when the skin becomes brownish and crisp.
8. Sprinkle salt on the skin bits and eat them.
9. The end.
Seriously. So easy. Ok, just a few things. You can turn the heat up on this to speed up the process. I choose the lowest heat possible because, even though these are the best fats to cook with at higher temperatures, the lower the heat for extraction the healthier the fat molecules will be after all is said and done. Also, I am lazy and the lower cooking heat allows me to pay the least amount of attention possible. That's my favorite thing.
One tip: the larger the pieces of skin, the longer it will take to extract the fat. Some farms sell only slabs of skin. I have purchased skins this way, and I used to cut them up into 1/2 inch squares. Totally not necessary. One day I didn't have time to cut the skins into pieces, but I needed the lard so I threw it in anyway... and it still rendered. It just took longer. So totally up to you.
One more tip: I keep a pint jar of lard next to my stove, and keep the larger quantity of lard in my fridge. It will keep for months and months in cool storage.
The last tip: There have been a few times where I've started this a few hours before bed, and realized it wasn't going to be done before I nodded off. No worrying here, though. The great thing is, you can turn your stove off, and leave it there over night. I know, I hear you. It totally sounds questionable... Until you remember that in bygone days people use to cook sausage, and then keep it fresh for months by submerging it in containers of fat. The fat keeps microbes from making anything rot! Genius.
P.S. Someday I'll add pictures to this post... sorry, I'm lame right now.