Looking good in a bikini does not qualify as a certification.
Before you sign a contract, ask for evidence of current certifications. Some of the best include those from the American College of Sports Medicine, the National Academy of Sports Medicine, the American Council on Exercise, and the National Strength and Conditioning Association.
Has the attention span of a 4-year-old
Before you hire a trainer, you need to spend some time performing covert ops. Take an afternoon to watch your potential trainer work with other people. Do your own workout, but position yourself within earshot so you can hear how the trainer acts and interacts with their clients. It may sound a little odd, but as long as you're in a public space and aren't crossing obvious boundaries, it's perfectly reasonable to observe, especially considering the amount of money you may spend on this person.