Although I recommend sizes starting at 17" X 22", the prints can vary in size according to your specifications.  The range of sizes may be 8 X 10 all the way up to 46 inches. 

A wide mat (such as 6" or more) for smaller pieces brings focus to the art nicely.  I recommend mats at least 3" wide for larger pieces.  All mounting materials should be archival quality to insure your purchase is not damaged by staining or contamination.

Some local professional framing businesses familiar with the process of framing photographic art include Studio 12 Gallery and Abend Gallery.