Do you miter each seperately or is it in one piece.
Example: a narrow border and then the larger one.

You can do it either way. If you sew the individual border strips together first it is real important to have a consistent seam allowance or the sides will mismatch on the miter. You also have to make sure to leave the tails long enough.

Sew the borders together, than miter as one.

http://i.b5z.net/i/u/1428381/i/Miterdborders.pdf

There are other tutorials out there, this is one of many.

Yes, sew the two borders together, then mitre as one border. That's what I would do - I don't like Y seams, so would rather do four than eight.

it can be done either way. however, my preference is to do it together. it does require matching the seams... but i only have to do the angle once

I prefer to miter as one. As Madquilter said, be sure to leave the tails long enough.

ditto to miter as one - its much easier to do this way

If you do it all at once then the miter is appealing because it is all in alignment. Also, it is easier to do a fudge factor this way and still have it look great.

I did a tute on it once but couldn't find it. Will PM it to you.

ali

IraJane just posted this tutorial the other day. Maybe it will help.
http://www.quiltingboard.com/t-159715-1.htm