Sand all of the boards you want to use down with 220 grit sandpaper. This will help remove any rough spots so you don’t end up with splinters if you rub against the wall.
Before you install the pallet boards, it’s important that you paint the wall they’re going on with a dark color. No matter how hard you try, the pallets are not perfect so there will be a gap or a bit of unevenness up on your wall. The dark wall color will hide those small gaps for you and you’ll be glad you painted it before putting up the boards. You don’t need to worry about doing a good of a job, just apply a quick, single coat.
You don’t need many materials to install the boards, just use liquid nails and a brad nailer. Start from the ceiling and work your way down. It looks best to change the pattern and apply the boards to your wall randomly so that it has a natural look to it.
The pallet boards aren’t all the same width, so you want to be careful not to get too carried away with installing the whole boards and cutting later.
If you end up with a small strip on the bottom of the wall, you might need to rip the boards down to fit. You can choose whether or not you want to keep the baseboard on the wall, but you don’t have to.
Here are some examples of some pallet walls: