My speakers have a removable bracket that attaches to the wall with 2 screws. I positioned the bracket, marked the screw holes, drilled a hole, hammered in 2 anchors, and attached the bracket with the screws. Wire the speakers to your jacks, and you should have sound!
Next up, I'd like to hide the power and HDMI cords. Luckily I have a power outlet below my TV, so I plan to cut a hole for a new outlet behind the TV, and wire it to the existing one below it.
For the HDMI cable, I'm going to install 2 "pass through" or "recessed media box" plates, one behind the TV and one behind the receiver area. This allows me to pass a wire through the wall, so if if want to add any components later I can use it for this as well.
update: Oops, forgot to update this with a link to the follow-up project, here.