First let's cover safety.
Lye is an extremely strong base and will cause severe burns. The first step of making soap is always getting out the baking soda and keeping it close by. Use it to neutralize the lye if you get it on yourself. You should wear safety glasses if you have them available.
(Note from WW - if you don't have safety glasses, get some! As a chemist I can assure you that splash-back is a common occurrence during any kind of formulation and/or mixing. You only have one pair of eyes - the $5 it will cost your for a pair of UVEX goggles is well worth the price)
Next take all your aluminum spoons and pots and put them away. Lye will eat holes completely through them! Use glass, plastic, or cast iron pots and plastic or wood spoons.
There are only three necessary ingredients to make soap: water, fat, and lye. Soft water like rainwater works best but anything wet will work. Here on this farm we always use lard for our fat. I'm sure beef tallow or other kinds of fat would work but I've never used them. Here in the sticks all grocery stores still carry Red Devil lye; its probably in the same area of the store as the drain cleaners. If it sits on the shelf next to Drano that should tell you something. Yeah I know there are dozens of recipes out there calling for salt, sugar, borax, oatmeal, olive oil... try those after you master basic soap.
The hardest part about making soap is getting the ratio of these three right. Here is the ratio that we use: 8 oz. of fat : 3 oz. of water : 1 oz of lye.
Now here is how to make soap.
Sound simple? It is but you won't need to exercise the day you do this because the stir part is a lot of hard work. Sorry to put some of you guys to sleep. If anyone's got questions I will be happy to cover them on- or offline. If the site host doesn't mind me using up so much space I could tell ya'll about a few other things we non-yuppie types still do.