I tried Pulse Fitness' free 14 day challenge recently, and it was a good experience. They first sit with you to understand your fitness goals. If you are interested, they make you sign an agreement up front, and just request you notify them before the end of the 14 day period if you are going to change or cancel.
They put you in groups of 1-4 (I experienced both during my trial) and the instructors provide the right amount of encouragement as well as spend time ensuring proper technique. Chris in particular was fantastic in helping a newbie through the exercises
Their rates are a little on the high side for personal/semi-private training, and ultimately I decided this wasn't for me, but I'm glad I gave it a try. I contacted them to cancel, and it was no sweat. I'd recommend giving this program a try to anyone who is interested!