Absent specific rules from the show committee, the show label should go in the lower left corner as you look at the back. The reason is simple...the white glove people will flip the lower right corner of the front and expect the label to be there.
Entry forms will tell you what to include on the label, but it's usually just the quilt title, your name, address and phone #, sometimes email as well. If the show is to be judged, the label is usually required to be temporarily covered (by pinning muslin over it) so the judges can look at the back stitching without knowing who the quiltmaker is.
If showing above the local level, I would strongly advise removing any 'personal' labels before entry. They're TMI and they raise the question of hiding faults. Not all shows require the same info on the label, so if you plan to campaign a quilt in several shows, make sure your label is replaceable.