Best way to integrate custom functionality

Hello all,

I am working on a project that involves searching through free-text  
fields and would like to add the ability to filter out negative  
expressions at a very simple level.  For example, the field may  
contain the text, "person has no cars."  If the user were to search  
for "cars," I would like to be able to intercept the results and  
return only those without the word "no" in front of the search term.  
While is is a very simple example, it's pretty much my end goal.

I've been reading up on the various hooks provided within Solr but  
wanted to get some guidance on the best way to proceed.

Thanks!

--Andrew