Great question Skye!
I'll only add my two cents worth on the bike I've been planning for quite a number of months now, the '73 Schwinn Super Sport frame I bought from el twe early last spring.
The first choice was the paint and theme/style. I decided to not redo the original opaque green and go with a custom color and theme. Which led to picking a color based on---
1) What color bike don't I have?
2) What color would I like to have?
3) Is there a color and theme I prefer that is different from what Schwinn normally painted Super Sports?
The second choice was which components to use. Since I basically had a frame and I didn't want to use the one piece heavy crank, I would replace as much of the original steal bits as possible. So I found myself asking these questions---
1) What kind of components would I use and which ones would work?
2) Which components would have the curb appeal to match Dr.D's paint and JR's decals?
3) How would I ride the bike and in what kind of terrain?
In the end this Super Sport will be very different from "PC" (period correct), but I will have had a great deal of fun, and it has been wonderful experience.
In 2008 I plan to pedal more and wrench less, if I can only avoid the temptation of going to the dump.