Ask for a recommendation on Facebook or LinkedIn first to see if any of my friends can recommend someone.
Google it to see who comes up in the search results first. If I can't find anyone I'll ask for a recommendation on Facebook.
Call, text or email a friend or colleague first. If I don't hear anything back soon I ask connections on Facebook or Linkedin who they can recommend.
Undertake a search using keywords in Facebook or LinkedIn.
All the above at it depends on what I need and how well I know people who might know who I need. If absolutely pushed the first 3, then the fourth option.
Follow references from material I find relevant