Most historians publish their work in books. So, for many topics in history, your best starting point is a good recent scholarly book. The easiest way to find that book is to ask someone else who is knowledgeable about your topic -- for example, your junior seminar instructor or spring JP advisor. But a thorough search of the library catalog is also essential. Here are some tips on finding books about historical topics in the Princeton University Library New Catalog.
Once you have a book in hand, read it. Alas, there are no shortcuts to this part of the research process.
While books are very important, historians also publish their work in articles in academic journals. And the easiest way to find journal articles is to search a bibliographic database that covers your topic:
Indexes books and journal articles on the history of the United States and Canada from prehistory to the present. 1954+
Print predecessor Writings on American History covering 1904-1954 is in Firestone's General & Humanities Reference (DR) Z1236.L331.
Indexes books and journal articles on the history of the world (excluding the U.S. and Canada) from 1450 to the present. Index 1954+
Consists of 2 parts: (1) The African Studies Companion Online contains entries covering guides and resources for African languages, Africa cartography and maps, African film, African studies journals, magazines and newsletters, media guides and news sources for Africa, the African press, African studies library collections worldwide, national archives in Africa, centers of African studies and African studies programs worldwide, awards and prizes in African studies. (2) The Africa Yearbook covers major domestic political developments, the foreign policy and socio-economic trends in sub-Sahara Africa – all related to developments in one calendar year.