It starts with draping pieces of fabric on a mannequin to get an understanding how fabric works and how to achieve a good pattern. It is essential and excellent.
Dress Pattern Designing: The Basic Principles of Cut and Fit
Basic (and working!) drafts for dress, skirt, blouse with dart manipulations, collars, and different kind of sleeves.
Just to be complete: More Dress Pattern Designing
Those books are classics from the 60ties. The more modern editions have supplements from Ann Haggar. You may get them cheap second hand.