In my experience using several search options or filters, it seems to be best to use radio buttons or check boxes to refine the search criteria. 

I was able to find an interesting study on [Visual Searching vs. Text Searching][1] which you might find useful.


  [1]: http://www.ala.org/ala/mgrps/divs/lita/ital/252006/number3september/fagan.pdf