A weed trimmer, like any garden tool, can make you more efficient if you use it properly. Safety is important, and a steady hand and quick eye will help you get the job done.
Be safe. Wear eye protection at all times. Weed trimmers cause grass, debris, rocks, sticks and anything else in their way to fly up and out, and you can easily be hit in the face and sustain eye injury if you do not wear safety glasses. Never use a weed trimmer when children are in the area. Never try to fix the head of a weed trimmer when the engine is running.
Keep the line short so that it does not extend past the guard on the head of the weed trimmer. Longer line will damage the guard and will create too much strain on the engine of the weed trimmer, which can cause it to burn up.
Keep one hand on the handle and one hand on the shaft of the trimmer to provide the greatest amount of control.
Use a shoulder strap for support, so that you're not taking all the weight and vibration in your hands as you use the weed trimmer. Shoulder straps clip onto the shaft of the trimmer and loop around one shoulder so you can distribute the weight of the trimmer as you use it. It reduces user fatigue.
Keep the throttle in the middle range. If you don't squeeze hard enough, you won't have enough power to turn the line fast enough to do the job. If you throttle too much, you may not be able to control the machine and you can burn the engine out faster.
Swing the head of the trimmer with a slow, smooth motion in an arc in front of you. Move the trimmer forward and step forward to cover more ground. Always look behind and to your sides before turning and using the trimmer behind you, to be sure you won't hit any obstacles.
Watch for hidden obstacles, such as wires, fence posts, metal poles, large rocks or bricks; a weed trimmer isn't powerful enough to eat through these objects and will bounce back upon contact, which can cause injury. Keep a wary eye out, and if you see an obstacle, turn off the trimmer, set it down, remove the obstacle, then resume use.