Mark the desired hole location on the concrete floor with a fine felt pen.
Measure the desired hole depth on a new long shank 5/32-inch masonry drill bit with a steel ruler. Mark the depth by wrapping a piece of masking tape around the drill bit shank. Clamp the bit into the chuck of a two-speed hammer drill. Set the drill to the low speed and non-hammering settings by twisting their respective levers on the drill body. This setting will help to start the hole accurately.
Position the point of the drill on the pen mark. Hold the drill vertically. Press the trigger in a series of brief burst until the hole is started in the desired position. If the drill starts wandering, tilt the top of the drill in the opposite direction to bring the bit back to the center point. Stop when you have penetrated about 1/8-inch.
Set the drill to the high-speed position and flip the lever on the side of the drill into the hammer setting. Place the drill bit in the hole and hold the drill in as vertical a position as possible. Do not apply any added pressure to the drill. Press the trigger to drill the pilot hole. Remove the bit after every inch of penetration with the drill still running to clear the flutes of debris and too cool the tungsten carbide tip. Blow the hole clear with an aerosol can of compressed air before resuming. Withdraw the drill bit when you reach the desired depth and clear the hole again with compressed air.
Mark the hole depth on a fresh sharp masonry drill two sizes up, and clamp it into the chuck. Repeat Step 4. Continue the same drilling process with progressively larger drill bits until you reach the correct hole diameter.