Imagine the person you're speaking to. If you're supposed to be speaking to the audience, imagine who they are--friends? enemies? the doorman?
Imagine where you are and the things that are around you.
Create a set by using real objects that are handy--chairs, benches, fake tree, etc.
You can use real objects for props, too--book, wallet, football, etc.
Be expressive--get mad or happy or sad or just have some attitude as you perform your monologue.
Movement & Gestures--use them. Don't just stand still while doing a monologue.
If there are stage directions—in parenthesis—in the monologue, use them or come up with your own. They're just suggestions. If a monologue has ellipses (three dots in a row), act as if you’re listening to someone else responding or speaking to you. But those ellipses might also just mean there's a slight pause. Read through the monologue and see if you're listening to someone or just pausing for effect.
Break a leg! (That's theater talk for "good luck." It's bad luck to say "good luck" in the theater so you say "Break a leg!")
What Mess
(holding a shoe, in bare feet; to audience) My mom thinks my room is a mess. I think it is a creative stew, a gumbo of inspiration. (pretending to point out the items) My clothes lay on the floor, on the bed and over the back of the closet door. By seeing all of my clothes at once, I am able to create unique combinations of layers and colors that show off my individualism. (looking under a pantomimed bed) There are plates under my bed that have been there for weeks and although I agree with Mom that some of the odors are strong, I am quick to point out that the colors and designs of the mold are scientifically valuable and I will get a good grade for them. (pointing out the items) The various books and papers that line the floor, desk, bulletin board and nightstand allow me at any moment to stretch my mind to new dimensions through the written word. Mom thinks I’m a pack rat just because my dresser, window sill, and shelves are lined with pieces of drift wood. I see architectural possibilities in each of them. Most kids my age don’t have crayons but I have mass quantities spread all over my desk. I’m ready when the hidden artist inside of me wants to come out. Under my bed are my basketball, blades, mitt, and soccer ball. My body has to have physical enrichment, too. My stereo is surrounded by CDs. What seems like chaos to my mom is really an organized blend of music styles for my listening pleasure. In spite of the brilliant mass of awe-inspiring odds and ends that are a part of my room, my mom says it’s a mess (brief pause) just because I can’t find my other shoe.