OK Karla, here is what I've been taught in a couple of classes and I've used the advice. It has worked out really well for me so far, AND it has made me much more conscious of making sure I have the "right" tool for the job.
All of these are good for cotton thread:
80/12 Microtex, 80/12 Jeans/Denim, 75/11 Quilting, 90/14 Topstitch
These are good for Metallic thread:
80/12 or 90/14 Metallica, 80/12 Metafil
Some of the difference in the needles are that the Jeans/Denim 80/12 are much sharper than the universal and they will more easily go through all the layers of the quilt, especially when using cotton batting.
The Microtex Sharp 80/12 is the best needle for quilting on poly batt..it will not dull as quickly and is meant for synthetic fabrics.
The Metallic or Metafil needles are recommended for use on rayon or with metallic threads due to the larger eye which will not wear the thread as much.
Some of this information came from Paula Reid of Batts in the Attic, and some of the information came from Libby Lehman.