* New file
When you start a new drawing, the software will ask you for a page size, landscape or portrait, etc. It's best to choose a setting you consider your pattern will position within.
In the screen shot below I'm going with an A3 paper, landscaped...

* Bring in the image to trace.
I've chosen a bird illustration as the subject. He'll become a frame less, flat, free hung panel.

So, we insert our picture file onto the art board. It usually needs scaling to fit our desire / page.
We'll trace from this image. Ideally we want to "lock image" on this one so that it can not be moved at all during our drawing process.
When using Adobe Illustrator, one can set up layers on the art board that make working with the drawing so much easier.

* Make use of layers for better control
The screen shot below shows that I have created 3 layers. The bottom one is our now locked subject layer I've called trace, the draw layer is the one we'll work with, and the text layer is for numbering the final pattern with. Each layer can be now controlled individually. For example our trace layer has been locked and dimmed to 30% and it is visible.

* Ready to learn vector drawing?
There is a bit to learn here, it's going to take some practice, however once you get the hang of it there will be no stopping you.

Some Youtube tutorials are in order here I think.... They are not mine, however they are the best that I've found so far.....

The screen shot below shows the beginning of the tracing task. Notice a few things going on here.
* The line is stroked with bright red from the swatch panel. It has a stroke of 0.5mm.
* The layer panel shows we are focused on the "draw" layer (it's high lighted blue), and the trace layer with our subject on it is locked.
* The lines I've drawn have anchor points and handles. You position curve nodes with the anchor points and the handles define how much curve is pulled between each anchor.

One continues to create new lines until all are in place. All lines need to be checked. Curves must not be too tight, the shapes they form have to be cutable in glass and the smallest shapes need to be cutable too.

At this point, I'll select all the lines and group them together as one object. Doing so stops you from accidently moving individual lines in the drawing.

It is now ready to colour in, so here is when I plan it's colour scheme. I use the "Live paint bucket" tool for this job and dump colour into each shape.

The next task is to number all the pieces so that each template piece can be identified.
On the layers panel, lock the draw layer and select the text layer. Now with the text tool, I place in the numbers.
Notice that the trace layer can not be seen behind the drawing. This is because I have clicked off the visibility option in the trace layer...

The final task is to save the file and to print the pattern to paper. When I'm using Adobe Illustrator, I do not need to save it as some other file type in order to make use of it.
If however I intend to share it with others, I will save a copy as a PDF file. PDF's can also carry security passwords, so if you do not want it to be opened or edited without your permission, you can do that.

When you are all finished, it is ready to print. I will print it twice to a light card paper. One is kept whole and used as the layout sheet. The other is cut into templates....

If your pattern is larger than your printers ability, it is best to save a copy as a PDF (high res) put it onto a memory stick and take it to a copy store for them to print....

Get started with Adobe Illustrator, link to free trial here

Good luck... :-)