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!")
BRAND NEW SHOES
I got brand new shoes. Aren’t they awesome? (looks at shoes) Wait! Is that a scuff mark? I hate scuff marks on brand new shoes. But no prob because I was thinking ahead. (pulls out a wipe) I brought a wipe and just like that (rubs wipe against shoe), my scuff is gone. (looks at shoe) Or I thought it would be. (sits on ground to rub harder on shoe) This is not working. That scuff mark is not disappearing! Maybe if I just…(rubs fast and hard). Oh, good. The shoe is just like new. (stands and looks at shoes) Wait! Is some of the color faded? Oh, no. I wiped away some of the color. I hate faded colors on brand new shoes. I need a marker. (exits)