Occasionally we're blessed with the right circumstances and dialogue to be able to deliver a killer one-liner, or a great punchline for a joke that was set up at the beginning of the scene. But that almost never comes from being the funniest guy or gal on the stage. It comes from teamwork - working with your fellow performers so that you have a feel for everybody's strengths and weaknesses - from cooperation - the idea that the whole scene benefits when everybody looks good - and from listening and reacting - since the scene is already made up, it's going to have some inherent ridiculousness in it, so let that naturally generate the funny.
So many times, students enter a scene and force a joke or a gag, and one of two things happens: the joke gets a great laugh, but then no one in the scene knows where to go from there; or the joke doesn't get a laugh, and the players now have to work harder to justify the poor offering and move the scene forward. Either way, it's more work on everybody.
So let's try this instead: enter a scene with a solid offering. Listen to your fellow performers and respond to them. When someone finds a joke they can set up for someone in the scene, let it happen then. Or, if one never comes, let the scene be about itself. Make your scenes good improv, not forced funny improv.