Here’s the data sheet for the LM386 IC with some example circuits:
Instructables has a simple how-to:
The schematic used in my project is a variation of this one from:
The only difference is that I added a 100nF from pin 7 to ground. I think it helps keep the noise down. There’s also two of everything except R1 and C1.
Wow, my wires are all way too long. It makes it very hard to get into a tiny box, but it works!