Prose can be either humorous or serious and generally a good prose is a little bit of both. To me Prose is baseline interp. It is as basic as interp gets. You tell your audience a story. The better you tell the story the better you tend to do competitively. While that sounds overly simple storytellers, truly great storytellers have been revered throughout the ages and while they make it look easy it is truly an art form.
Prose does tend to be more serious than humorous but really the best prose are a combination of humorous and serious and the performer takes us on an emotional roller coaster ride. We tend to see inner conflicts played out and realizations made about one's self and the human condition. As with all good literature we should grow from the experience of the literature. When I am done watching a good prose I should think "I get it" or "Now I understand why..." The characters need to be people to whom we can relate and empathize. Believable and deep characters are far better than slick, polished characters with a cool accent and the depth of a wheat thin.
You want to find something with a good story. Something with a beginning a middle and an end. Too often we find great beginnings, great middles and then the story just stops. There is no sense of resolution or conclusion. There are some interp techniques we can employ if you find a piece you really like that doesn't end well but in general it is better if you can find a piece with closure.
Good prose usually centers on some kind of conflict. Not necessarily between two people but often between ideas or ideals. Someone is coming to terms with a change in their value system or with a change in their relationships or a change in their outlook on life. They learn to deal with hate or vanity or jealousy, or love or loss or who knows what else. But we them experience that journey.
First Person prose tends to work best. This is partly because you get a better/more direct connection with your audience. It is you (the author) talking with an audience in what usually seems like real time. There is greater immediacy and more of an opportunity to build a para-social relationship with the character.
Find something you enjoy. That is probably true of all the interp events (and public speaking for that matter). But the difference between a talented competitor with a great piece and a talented competitor with a great piece they love performing is the difference between the one and the three in many final rounds.
Find something that fits you. That doesn't mean that if you are a minority you can only run pieces about being a minority. It doesn't mean if you are gay that you can't compete with a piece in which you play a straight person (or vice versa). But it does mean that if you are 5'10" and 120 pounds you probably shouldn't choose a piece where you protray someone who is chronically, morbidly obese as your first choice.
Find something that challenges you. There are competitors who chose the same kind of literature every year. They have learned to perform one persona very well. But they are not learning or growing with each new piece. They find something they are comfortable with and they do it. It is safe, it is easy to get to competition reeadiness quickly and it is something with which they will likly experience some success. But trophies are not the most important part of this activity. Trophies are a byproduct of what we do. This is an activity about learning and growing and developing into more than you were. You can't do that by doing the same thign over and over.
There are just too many prose out there for me to provide samples here.
I would also encourage you to read this oral interp at the college level a