Are there any rules for gelling flash when you have both tungsten and florescent light in the room? What about tungsten and daylight?

Should I be combining a CTO and florescent gel or just picking the one that is most prevalent and gelling for that?

Also how do you know when to use a 1/4, 1/2 of full CTO? What about Full Straw?

Thanks!

Hi Lauren. Strobist is a great place for little tips like that. here is a link to an article about gelling flashes. Essentially it's best to go w/ the dominate light color.
http://www.strobist.blogspot.com/2006/03/lighting-101-using-gels-to-correct.html

I usually try to gel for the most dominant light, as Brian mentioned. Whenever possible try to simply turn off the fluorescents though... they are nothing but trouble.

When I gel for incandescent light, I use Full Straw because it converts slighty yellower than CTO. Full Straw better matches a regular household light bulb's color temperature.

You would use the 1/4, 1/2, etc. if you wanted less correction and wanted the background color to contrast a little more... either blue or amber, depending on how you gel the flash.