In my book, I suggest that all aspiring actors have three monologues ready to go at all times. One of these is to be classic which is usually Shakespeare. But I get lots of questions about how to understand and play the Bard's plays, so I thought it a good time to discuss just that.
There are some plays which are much easier to understand than others. As You Like It, Twelfth Night, and MidsummerNight's Dream are pretty straight forward though the last is pretty complex with all its sub plots. So the first thing to do is to pick a play that is pretty easy to understand. Then you will need an annotated script of the play that has plenty of footnotes or marginal notes to explain archaic words and expressions and contemporary references. Also keep a dictionary at hand just in care there are some words you don't understand that are not explained in the notes.
Now the real key to reading Shakespeare is the punctuation. If you are having a problem understanding the meaning of the speech, I suggest you approach it sentence by sentence. Periods, question marks and exclamation points indicate the ends of sentences. We never endstop reading verse because that interrupts the flow of ideas. (Unless, of course, there is a period, question mark or exclamation point at the end of the line.) Once you have the sentences separated, follow the commas, semicolons and colons to learn the meaning and to speak the line naturally. Commas indicate pauses and denote items in a series or set off a parathetical expression. Semi colons indicate that a related idea or further explanation follows, also giving the reader pause. And colons indicate that explanation follows which could be a series or a restatement of the idea at hand. Colons indicate pauses longer than commas and semicolons and shorter than end of sentence punctuation. Sometimes just reading the line following the punctuation will make it understandable.
Finally, after figuring out what it all means, you have to act the speech. Remember like all speeches, a monologue (or long speech) contains the emotional and physical reaction of the character to what has just caused him to say it. And, as it is a long speech, often what the character himself says will be the stimulus for what he says next. Suit the action to the word, the word to the action and you are performing Shakespeare like a pro!