Keep Your Thesis Balanced
Keep the thesis balanced. If it's too general, it becomes vague; if it's too specific, it cannot be developed. If it's merely descriptive (like the bland example above), it gives the reader no compelling reason to go on. The thesis should be dramatic, have some tension in it, and should need to be proved (another reason for avoiding the obvious).
Too general: Edna St. Vincent Millay wrote many poems with love as the theme.
Too specific: Edna St. Vincent Millay wrote "Love is not all: it is not meat nor drink" in <insert date> after <insert event from her life>.
Too descriptive: Edna St. Vincent Millay's "Love is not all: it is not meat nor drink" is a sonnet with two parts; the first six lines propose a view of love and the next eight complicate that view.
With tension and which will need proving: Despite her avowal on the importance of love, and despite her belief that she would not sell her love, the speaker in Edna St. Vincent Millay's "Love is not all: it is not meat nor drink" remains unconvinced and bitter, as if she is trying to trick herself into believing that love really does matter for more than the one night she is in some lover's arms.