You can combine your author or work with specific theoretical approaches. You'll find some have been treated more broadly than others, given an author's historical period and cultural milieu. For example, taking an ecocritical approach to Kate Chopin's The Awakening may yield very few sources, whereas combining "awakening AND Chopin AND feminism" in a database like JSTOR, Literature Resource, or MLA, will bring you multiple results written over many decades.
All databases use the same or very similar search mechanisms to both limit and expand your results.
Place several words within quotes to search those exact words in that exact order.
"masque of the red death"
Truncation and Wildcards
Use a symbol (usually * or ?) to search all words that start with entered letters.
fem* searches for feminism, feminine, female
eco* searches ecological, ecology, ecocritical, ecocriticism, economic, economy, economical, etc.
*hist* searches ahistorical, historicism, history, histories
AND searches for both terms, OR searches for either term, NOT omits a term.
"herman melville" AND slav* NOT "benito cereno"
"queer stud*" OR gender