Each child comes with its own individual 'set of baggage' and you never stop learning. Their trust has been broken time and time again and they anticipate that you will be no different. And don't think for one minute that, since you raised teenagers of your own, that you are ready for a foster teen. You will disillusion yourself, setting yourself up for failure before you begin.
Nothing prepared me for fostering teens!! I was given nine weeks of training from the Children's Home Society before taking my first foster child. There was a great deal of information to digest in a short span of time. It left me with the innocent impression that I was ready to tackle the job.
The class was executed beautifully and all was done to teach us as much as possible in a classroom environment. However, until you have actually encountered the 'foster teen', it is impossible for you to really get an accurate view of the situation at hand.