Indecent Exposure 18: Invaluable extras

I generally avoid ever using a flash, choosing instead to go with fast lenses and if needed higher ISOs, but have recently decided that there are just some times that you need a flash. This lead me to find that buying a flash is a lot more complicated than I expected. Could you give a quick rundown or explanation of the Guide Number, and how do I try to determine how large (or small) a Guide Number I need?

Tip I recently learned--If you are using Photoshop Elements (or presumably CS3...though I do not own that), you can edit your JEPG pictures in Adobe Camera Raw. From the Editor (or File Manger) Screen Go to Open File As, when the dialog opens choose Camera Raw...it will still show you all of your JPEG pictures, simply select the picture you want to open, and it will open it in Camera Raw. When in Camera Raw, use the "Vibrance" Slider which gives you much finer control and nicer results than the standard Saturation Control. Of course, do I need to point out that I love the show? Keep up the good work.
Jay Romeo aka JayMonster on the CNET forums