I like to buy a little extra yardage when purchasing fabric for a specific pattern--great for mistakes, but also great to make some "Pre-Cuts" of your own for future projects--depending on how much extra, you can cut 2 1/2" strips or 10" squares (which can be sub-cut into charm squares), or half yards which make two fat quarters.
I just discovered this address
to make easily some biais tape. It is a tutorial with images. First, you have to make the paper tool, and then try it with your fabric. I did not make it yet but plan to do this instrument as biais tape is always very useful for the finition of everyday garnments. There are more interesting ideas in the site.