Make a sketch depicting the size of the concrete area you plan to groove or score. Decide on the scoring pattern and indicate this on your sketch.
Transfer the pattern from the paper to the concrete. Use a tape measure and make reference marks around the perimeter. Snap chalk lines between these marks to complete the pattern.
Attach a diamond-tipped masonry blade to your circular saw. Adjust the saw to cut at a depth of 1/4 inch. Tear off strips of masking tape and place them on the bottom of the saw. This minimizes the amount of scratch marks left on the concrete by the saw.
Position a straight edge, such as a 2-inch by 4-inch piece of lumber, along a reference line. While scoring, the side of the saw will rest up against this to ensure a straight line. Have an assistant stand on the lumber to keep it from moving.
Put on safety goggles and a dust mask. Turn on the saw, start at one end of a reference line and run the saw up the line. Be sure to keep the saw next to the lumber. When one line has been scored, repeat this process for the other lines.
Sweep the concrete with a stiff-bristled broom once all the scoring has been completed.
Complete the project by hosing down the patio's surface to wash away all of the remaining fine dust and debris.