How do I apply gold foil?

Very carefully. Here is a tutorial - http://www.ehow.com/how_5028445_apply-gold-leaf-te...

And here is a goofy video - http://www.graspr.com/videos/How-to-apply-gold-lea...

There are different kinds of gold "foil"... there's gold "leaf" (the link given before me showed one way of applying that) which is very-very thin, and then there's gold foil (also called heat transfer foil) which is thicker and also has a plastic backing; it's made from plastic rather than real metal like the leaf.**

Metal foils and leafing come in many different "metallic" colors.

(many people interchange the defintions and terms though, or don't know the difference, etc.)

**most metal leafing isn't *real* gold or silver, etc., though unless you pay a lot of money...it's generally "composition" leaf which means it's aluminum or copper, etc., then perhaps also dyed

Metallic leaf can be adhered with "sizing" glue or with anything that's tacky or adhesive. Some of it may need clear sealing since it may oxidize over time (usually with a water-based clear sealer).

Metallic foil can be adhered to something tacky (the have the clear plastic backing "pulled off"), or it can be adhered using heat (like inside a photocopier or laser printer, on paper) or on fabric/clothing with an iron or heat press, etc.

You can get more info about those materials at my site though my site is primarily about using them both on polymer clay... some of the info and the links would still be helpful though:

http://glassattic.com/polymer/leaf.htm

Or you can do searches for metal leaf and heat transfer foil too:

http://www.google.com/search?q=how+to+metal+leaf

http://www.google.com/images?q=how+to+metal+leaf

http://www.google.com/search?q=how+to+heat+transfe...

http://www.google.com/images?q=how+to+heat+transfe...

I don't know. I don't even know what you are talking about. I only answer when motivated