Pick a spot in your yard that receives most of the afternoon sun. Most herbs need full sun to grow.
Use branches or other markers to plot the bed's position. Move the markers around until you have a bed shape and size that suits your needs.
Measure all sides of your bed outline so you know much how lumber to buy.
Select the type of wood you want to use. A more durable but more expensive option is cedar. Pine is cheaper, but also probably won't last as long. Plan on buying only untreated wood, or wood that has been treated with a sealer certified as food-safe.
Buy lumber in the lengths needed for your planned bed. For example, a 6-foot by 2-foot rectangle raised bed requires two 6-foot lengths and two 2-foot lengths. Each piece should be the same width, preferably 12 inches wide to accommodate enough soil, and the same thickness, at least 1 inch to make a sturdy frame.
Place one longer piece of wood perpendicular to a shorter piece to form an "L." Nail the two pieces together with two to three nails. Repeat with the remaining short piece at the other end of the long piece of wood.
Line up the remaining long piece of wood to create a rectangle. Hammer nails into each side, creating the bed frame.
Lay the frame in its intended spot and use a level to ensure it sits evenly all around. Dig small trenches or use a rubber mallet to sink the uneven parts into the ground. Ensure every part of the bed is touching the ground.
Position the stakes -- which can be wood, metal or another material of your choosing -- at the four corners inside the frame. Use stakes that are about 2 feet long. Hammer the stakes into the ground so the top of the stake is even with or slightly below the frame of the bed. The stakes help anchor your bed in place.
Determine the number of cubic feet of soil you need by multiplying the length of the bed by the width, then multiplying the product by the height. Fill the raised beds with the best soil mix for the herbs you wish to grow. Usually, this mix will include potting soil, some compost and peat moss, and possibly clay or sand. Fill the bed until the soil mix is even with the top of the frame.