Vlookup and automated number column

I have a Vlookup function in one column and I have it set up to return information when certain criteria is met by selecting information from an adjacent cell.  If no selection is made in the adjacent cell or in the rest of the row, my auto-numbering column still populates a number even though the entire row does not contain any information. Is this caused by the Vlookup function trying to search for its specified information?  How can I stop the auto-numbering column from populating?  I have also tried nesting the Vlookup function with the IF(AND function to meet additional criteria before the Vlookup function searches for its information.