Install the diamond blade on the circular saw. Adjust the cutting depth of the saw to be a quarter inch less than the thickness of the brick paver. For example, set the saw to make a 1 3/4-inch cut for a 2-inch thick brick--this will make sure you only cut the brick, not your work surface. Check the instruction manual for directions particular to your saw.
Use a ruler to measure the brick paver and a pencil to mark where the brick should be cut. Use a carpenter's triangle to ensure a straight cutting line: line one edge of triangle along the edge of the paving store and use the other edge of the triangle to draw the cutting line.
Put on a dust mask and safety goggles to protect yourself from dust and flying debris. Place the brick on a safe cutting surface, like an extra paving stone. Hold the brick firmly, but make sure your fingers are not in danger of the saw blade.
Cut the stone, following the pencil mark and pushing the saw away from you. Gently break the stone along the cut edge with your hands, or tap lightly with a rubber mallet to finish the cut.