Searching Custom Parameter Log

Hello,

I want to record the search keywords from my search form added by the plugin for classifieds for custom search query parameter “q” and for select list in form for location, custom query parameter “l”, it uses search query parameter “?q=”.
Where I need to make changes in plugin files, so I can track the search terms with custom parameter for “q” and “l”.

your help is appreciated

Thank in advance