Develop your profile: The variables that define "who you are" will be of interest to funding agencies (academic status, gender, race, religion, origin of birth, skill set, academic interests, artistic interest, passion).
Search by subject: Most books or websites on funding sources have a subject index/search. Read the descriptions and narrow your selection to those that fit your profile.
Identify likely sources: Professional associations may advertise fellowships for graduate students or postgraduates. Foundations have as their mission to provide funding for either individuals or institutions all in the name of supporting good causes or projects.
Use portals of information: the school you attend or will be attending will list opportunities in their financial aid office or website. The library collects books on funding sources and provides links to relevant agencies and websites.
Excellent resource for finding opportunities on competitive research grants from government agencies. While most opportunities are for established and full time scholars, one can find opportunities for graduate students also.
Guide to thousands of 2- and 4-year schools in the U.S. and Canada. Covers the expected listings and detailed descriptions, degree programs offered, scholarships, and occupational education programs. Updated yearly.