Underline key words in the text and look them up in the Oxford English Dictionary. Identify the sense in which you think the speaker is using the word. Identify groups of related key words. Use the full 20-volume edition of the OED, and be sure that the definitions you choose to focus on were current during Shakespeare's lifetime. Focus on the concrete and literal sense in which the speaker is using the word, rather than the metaphorical or thematic resonances that the word may have in the play.
Topics Identify the main topic of the speech.
Account for every line, including and especially any that seem odd or out of place. This will be a clue to the speaker's objective in the speech. Mark each time the speaker changes minor topics in the speech. It is unusual, though not impossible, for a speaker to change topics mid-line. These beats all serve and inform the character's action for the speech.