The best way that I've found for helping someone get into any physical thing (from weightlifting to parkour to sports) is to give them a taste of it and let them in on the benefits of the training and fitness aspects, without boring them to death with details. In the end, you'll only be able to recruit people that really want it anyway. Some people just aren't ready for things like parkour, others don't have any desire to do anything physical at all. You can't force people, but you can give them the tools to make a more educated decision.
There is also a different approach depending if it's a male or a female. This isn't always true for every man and every woman and I don't mean to sound steriotypical but, most men want to see and do the big jumps and grabs that require a large amount of strength and will be more drawn into the discipline with the fitness benefits of strength, real world application, and versatility, where as women generally like the more gracefull aspects of parkour and will be more drawn into the discipline with the fitness benefits of a more slender and lithe body.
These are just some things that I've noticed from spending around 10 years in the physical fitness business. There is no perfect way to make people want to do things. In the end, there are those who do, those who teach, and those who watch.
It'll be interesting to see what some others say also. Hope this helps.
