In the attached test_bag.blend file, the bag has several parts: front, back, base, etc. How does one select an individual "part" of the bag without selecting others? For example, select only the front or back or interior part.
Further, I would appreciate a link to, or in depth tutorial of, selecting/selections; -- beyond the basic tutorials on utube, et.al. TIA
There are two ways in edit mode (↹ Tab):
Press L while hovering the mouse over the part of the bag you want to select. This will select all the geometry which is connected to the part under your cursor.
Select some geometry (e.g. with 
RMB), then press ⎈ CtrlL. This will select all the geometry which is connected to the existing selection.
If you want to separate the parts into separate objects, then press P> Loose parts in edit mode. This will separate disconnected parts of the object into their own objects.
You should first remove any duplicated vertices Edit Mode / Tools-Tab - Remove Doubles.
Selecting all A and separating P Loose parts would lead to something like:
If you want to select front and back switch to front view orthographic view Numpad-1, Numpad-5 and use Box select B, make sure that limit selection to visible is enabled (highlighted icon in the last image)
Assign the selection to vertex group, this enables you to select them later e.g.
repeat that for all groups you need in the appropriate view (the bottom is easier selected by the 'select linked' method gandalf3 has already described).
