Read the Classic and Vintage forum for a few months and you will get to know what the better vintage components are.

Some of it is personal taste, but there is some agreement by most on some components...

As far as frames, generally lower weight = higher quality... Also, they will usually have the better components.

If in doubt, physically pick up a bike... if it is light, then the frame and components are probably high end.

Forged dropouts are a sign of a better frame as well...