Xanax is ten times stronger per mg than diazepam, yes. Forging prescriptions is something you could give me advice on..
Well it depends what nation you live in. Unfortunately, I think the US (for certain), Canada and a few other western nations have implemented electronic prescriptions making this impossible.
Though I think that is only in some states.
WHAT I did was forge my original but legitimate prescription (handed to me by a GP) for x50 tablets of 2mg diazepam. I got that one filled then put the prescription in my scanner/printer. I got a portable version of Adobe Acrobat Professional from thepiratebay (more advanced then Adobe Reader. has scanning/image editing/OCR)
After scanning the prescription with my printer in the portable Acrobat software, I used OCD (Object Recognition) to make it high def and allow me to print the ("template" - name, logo, and GP address) while blanking out the lines to have only a "blank script".
I then printed it on an A4 page and used scissors to cut out the edges, trying my best to make it look normal (keep in mind that prescription paper is written on A5 paper which is half of A4 so you could half A4 paper then put it in your printer assuming it supports A5 paper).
Lastly, I practiced my handwriting as best as possible. It work x5 times, only got caught on the 6th time.