1.  There are two search methods included on the search page.  The first search contains the first 8 fields, while the second search is using the ISBN # or the part #.  If you enter an ISBN or part number, all other information is discarded. 
2.  You can not use wildcard characters in the ISBN search and expect reliable results.  Wildcards may be used in the Title or Author fields, but is not necessary unless it is used between letters/words because the search adds the wildcard to both the front and the back of your search term.  Wildcard substitutions for ASP/ADO:
  Use  %   NOT  * 
  Use   _    NOT  ?
3.  When you choose more than one field to search on, both conditions must be true in order for a book to be in the results.  If you get no results, double check your spelling or try dropping a field.