I used an el cheapo website builder to make a template. It is not too fancy, just makes it so my auction text is in different colors and in neat looking boxes. I include a generic shipping and handling section filled with my most common shipping terms. (Most items I sell I ship for $2 flat rate)
I then took that page and did the copy between the body tags like mentioned before, and saved them in NOTEPAD as a TEXT File. Why? Because it is a lot faster to open up and copy again and again.
When I need to list a single item on eBays SYI form I can quickly cut and paste into SYI, add a description within the description cell, and double check the shipping costs if need be, then continue with the normal listing process. YOu can put something in the description cell during the design proccess to make it stand out more in the text format, such as ##### or @@@@@@@.
This proccess has worked well for me, and dresses up the listing without going overboard. No one likes to wait 5 minutes for the sparkly text, background image and sound, and cursor trails to load! I also avoid changing the fonts just incase the user does not have that font loaded, otherwise their text may look out of wack.