Regarding UV maping and Face Gruoups Selections there seems to be the general misconception that you can’t save your face groups selections on Blender.
Must people already know that from within the Face Select Mode (Potato Mode) you can switch into Edit Mode and whatever selection you do while in Edit Mode is passed back to Face Select Mode when you exit the Edit Mode.
Well… Did you ever wonder why Material Index Groups (that are nothing more than face groups with a common material on them) have those little ‘Select’ and ´Deselect’ buttons there? Sure they come handy for later modification of the material index but that is not all about them.
Do this: Before starting the UV unwrapping job, cut your mesh by creating as many material indexes as you need, you can even assing each one a different color so you can be shure that there is no face orphan. Once you have the mesh all cut and sliced (so to speak) you enter in Face Select Mode, then switch into Edit Mode, selec the index containing the faces you want to unwrap, press ‘Select’, leave Edit Mode and VOILA!!! there you just have an entirely usefull face group waiting for you to unwrap. No more manual (and unprecise) face selection is needed.
If you later need to change the mapping of those faces don’t fear, just make shure there isn’t any face selected on Potato Mode, do as you did first (enter edit mode, select the index, exit edit mode) and there are your very same faces selected again with the UV mapping you already assigned to them.
Another benefic of have precise face selection groups is that, inicially, you don’t have to worry about UV coordinates overlapping, since you know have the way to selec ONLY the faces you whant to. For example, you unwrap all your faces by groups and when you are done you can start thinking about scale and position withing the texture map, not like before when you have to solve those things as you go.