There are several ways to copy clothing.
1. Draft a pattern. This requires a skill set that is usually learned in a class or as an apprentice to a tailor. There are some good blogs on this topic and I am only just beginning to branch into this method.
2. Trace an exact copy of the garment. This can be done in a way that preserves the original garment by tracing it on paper, transferring all of the design element markings, darts, seam allowances, trims, pockets, button placement, zippers. This requires intermediate to advanced knowledge of garment construction and accuracy with tracing and transferring marks. I might write a how to on this sometime, but not today.
3. Deconstruct the original garment to get exact pieces for a pattern. This is what I am going to show you today.
Step 1: Tools and What you need to get started
1. Blue jeans you are willing to take apart. When I decide to deconstruct a garment it is something I do not plan to put back together.
2. A seam ripper.
3. Place to store the pieces as you remove them. A one gallon zip close plastic bag will keep pieces together.
4. Time. Don't try to hurry this process. You are studying the garment as you take it apart.