Do you sign your quilts before you quilt them or after?

After I quilt them.

after

after, I slip stitch the label on the back in a corner.

I've done both.
If you put the label on before quilting, it cannot be removed easily. I have even inserted it in the back and made it part of the back of the quilt.

Before because I machine embroider my own designed label on the back

depends on if it is going to be shown or just given away. If shown, follow what the rules state, if given away, it depends on where you are giving it, to a family member, friend, or to a local charity. If a charity, ALWAYS quilt the label on...reason, it keeps it from ending up on ebay!