Determine the height of your wall and use that measurement to figure your footing width. The basic rule of thumb is that your footer should be as wide as half the height of the wall. So, if your wall is 10 feet high, you need to have a footer that is at least 5 feet wide. It should also be anywhere from 4 to 30 inches thick, depending on if you are building a cosmetic wall or a foundation wall.
Dig a trench for the footer. Use a tape measure to ensure that you are digging down sufficiently deep and wide for the footer. Include width for the form boards. Cut the boards down to size with the circular saw. Measure and mark them with a tape measure and pencil. Nail them together with the hammer and nails and place the forms into the footer trench.
Mix up a batch of concrete mix in your wheelbarrow. Shovel the mixture around for several minutes to achieve the proper consistency, according to the instructions on the bag. Dump the wheelbarrow into the form boards and fill them, according to the depth for your specific wall. Repeat the process as necessary until you have enough concrete in the boards. Let the footer dry for 72 hours, remove the boards and build your wall.