Push the "lock off" button, located on the handle of your Ryobi trimmer, to either the right or left. Pull the switch trigger to start the trimmer. Do not release the trigger until you are done trimming.
Place your right hand on the back handle and your left hand on the handle positioned on the bar. Keep your grip on each handle firm to maintain control of the trimmer.
Tilt the head of the trimmer slightly towards the grass you will be cutting. Lower the trimmer towards the grass until just the tip of the nylon string is cutting it. Do not push the trimmer head into the uncut grass.
Cut the grass to the desired height. If the grass you are cutting is very long, work from the top of the grass down, taking off small bits at a time, to avoid the grass wrapping around the trimmer head.
Feed more string out of the trimmer head by releasing the switch trigger, waiting for about two seconds and then pulling the trigger again. This will release about 1/4 inch of string.