I am not a traditional Pattern Maker. I have drafted patterns and I can draft patterns, but I've only taken one course through an adult education program.
I'm more likely to knock off a favorite garment or manipulate an existing pattern. Lucky for me a former employer/current friend has an Independant Pattern Company, Christine Jonson Patterns , and I can use the patterns to my hearts content. I am particulary fond of her patterns because they have comfortable armholes and tried and true fit from her days as a retail seller of clothing. They were mostly drafted for cotton-lycra fabrics, but I don't let that little detail bother me!
I use patternmaking books like "Patternmaking for Fashion Design" by Helen Joseph Armstrong for guidence and inspiration. And I also like the Built by Wendy book "Sew U", by Wendy Mullen, in spite of the sewing imperatives (my pet peeves- see earlier posts) because it encourages experimentation and creativity.
My approach to drafting is also not traditional, I'm inclined to leave the ruler on the table and redraw a line by hand to get the fit I'm looking for. Rules be damned! As far as I'm concerned the style and fit of a garment is limited to the width of the paper (there's always tape!)or ones imagination and not some set of rules established- how long ago?
Production sewing has also been helpful because I've learned what the pieces are supposed to look like. Tracing out the patterns before you make them is also particularly helpful because it makes you look at the pieces several times before you make the garment.