Employ a neighborhood teenager as a favor the kid, his parents or because he genuinely is a hard worker and you genuinely need yard care. Expect to pay more than minimum wage to get the teenager to value his job. Consider paying per job rather than per hour to keep your new employee motivated to get the job done quickly. Monitor the work to make sure it's to your liking before payment.
Take some time to remember what it was like to be a teenager with hormones, homework and your parents yelling at you to get a job. Take into consideration that your teenage employee will probably need motivation to complete her job well and value the time she is investing. Make a decision on whether you will pay your employee by hour or by job. If you are paying by job, she will likely work faster. If you are paying by the hour, she might figure out she can make more money by slowing down.
Many employers believe $10 an hour is a fair rate for yard work. Pay by the yard or job for a possible smaller payment. Offer $25 for mowing and trimming a large yard and $15 for trimming the bushes. Decide on what you are willing to pay per job and be ready to bargain. Some motivated teens set their own prices and run their own businesses. Expect to pay more for these teens, who may be running a legitimate business and paying taxes.
Take a glass of water or lemonade out to your yard worker as an non-intrusive, non-threatening way to find out if they are working hard or slacking off. This is especially important on a hot day so your worker does not dehydrate. If his work ethic is less than what you are expecting, ask him how much longer he will be and clearly tell him your expectations. At least for the first few times, inspect the yard to make sure it is to your liking before paying him.