Joanna Williamson is an ideal trainer. I worked with her as my first-ever trainer for most of two years (meeting once a week), starting about four-and-a-half years ago. (She left my gym, or I'd be working with her still.) I wanted to lose some significant weight, build my strength for injury protection, and work my way into the top 10% for my age group (which my doc says I've done). I've met all these goals, and I'm now into a permanent maintenance routine.
(1) She has a wonderfully encouraging attitude. Nothing at all like Jillian Michaels. She's a great athlete herself she's very strong and also runs marathons but this was always a real positive, not something that made you feel like you'd never measure up. She understands how hard exercise often is (and she makes it challenging), but she's great at helping you enjoy it. She really makes it interesting and fun.
(2) She's very knowledgeable about anatomy and physiology, if you like to learn how various things do and don't work (as I do), and she works to keep her knowledge current.
(3) She has a huge variety of exercises to teach you, so you never get bored, but she's also great at helping you build an exercise plan tailored exactly to your needs (including age and injury status), so that you can work out effectively on your own.
(4) I lost about 25 pounds in the first 18 months, and have kept 90% of them off. And I've kept doing three strength workouts a week (in my late 60s), pretty much through thick and thin, with what feels like permanent pleasure.
All in all, I only wish she still worked where I do. I've had a variety of excellent trainers since she left, and she's still the best.