Draw a sketch of your land. It does not have to be completely accurate or to scale, but it should correctly represent the shape of the land.
Mark off areas of your land in rectangles and triangles. Start marking off the larger square, rectangular and triangular areas of land. Divide the irregular shapes with curvatures into smaller rectangles and triangles.
Measure on your land the lines represented by the each side of the shapes you used to divide up your land with a distance measuring wheel. Start from one corner of each edge and plant your measuring wheel firmly in the ground. The measuring tape should unravel as you walk. When you reach the other corner of your edge, take the measurement in feet and note it on the appropriate place on your sketch. Repeat until all the sides of your shapes are accounted for.
Multiply the width and length of each rectangle or square of land to find the area of that piece of land. Note the area on the sketch. For each triangle, multiply the base of the triangle by the height and divide by two. Note the area on the sketch.
Add all the values together to figure out the total square feet of the land.