Whether you are altering a pattern and retracing it or making a new pattern from scratch, we cannot stress this enough:

Label and date your patterns.

Label and date your patterns.

Label and date your patterns.

Ok, got it?

The thing is that as you work, you are going to be developing patterns and shapes and then forget their contexts.  You don’t think you will, but then 2 years have passed and you pick up that pair of pants you started and… where was I again?

If you label and date your patterns you will find that you will have an easier time picking things back up from your project stack and getting back into it.

It is going to keep everything neater if you trace out the new shape onto paper or cardboard, too… but that is a rant for another day.