|Peggy has you come in with a muslin completed to her specifications (extra seam allowances and marking). The pattern you use should be very basic, no pleats, but it does not have to be her Silhouettes pattern.
At the class, you buddy up with another attendee. Following Peggy's step-by-step instructions, you drape and pin-fit each other and mark corrected seamlines on the muslin. Trace off the muslin when you get home and you have your personal perfectly-fitted pattern. Peggy personally checks everyone's fit, so don't worry about what will happen if your buddy does a bad job. (My buddy was fab!) Peggy also gives a lot of general information and takes questions. She also explains how to adapt your fitted muslin to any pants style.
End results: a better knowledge of how pants work (thanks to the hands-on fitting experience), my worth-its-weight-in-gold muslin, and the ability to repeat the process again for myself or anyone else I ever sew for.
If you take this class, here are my tips - 1. Be sure to take lots of notes. Peggy will be giving you more info than you can just absorb. 2. I think it's a good idea to make your muslin in pants-weight fabric (similar to what you'll be using for wearable pants) rather than real muslin; you know how fit can change when you make a pattern in two different fabrics.
I wear pants all the time, but never had nicely-fitted ones prior to this class. They have all been replaced with pants that fit and (my classmates tell me) make my ample butt look cute! Well worth the $$ to me.