Billy Wilder is considered one of the greats. You may not know who he is by name but his work has endured generations and influenced the majority of the film makers today. Especially Comedy. AND his ability to balance drama with comedy is a marvel to witness.
Take The Apartment. A lonely man loans his apartment out to his bosses so they have a place to cheat on their wives yet he is in love with one of the woman. In the end amidst a broken heart she attempts to commit suicide but the main character saves her. What a slugline, eh? That can't be a comedy. Well, it is! and a classic at that. Shirley MacLaine, Jack Lemmon. Giving you characters you relate to and feel for only raises the ability to make the funny.
Cameron Crowe, director of Almost Famous, interviewed Wilder some years ago and was able to pull a list of screenwriting tips that are still true today.
I especially like Tip #6. If you haven't given the right information in the first act then the third act is never going to work.
Billy Wilder: 10 Screenwriting Tips
1. The audience is fickle.
2. Grab 'em by the throat and never let 'em go.
3. Develop a clean line of action for your leading character.
4. Know where you're going.
5. The more subtle and elegant you are in hiding your plot points, the better you are as a writer.
6. If you have a problem with the third act, the real problem is the first act.
7. A tip from Lubitsch: "Let the audience add up two plus two. They'll love you forever."
8. In doing voice-overs, be careful not to describe what the audience already sees. Add to what they're seeing.
9. The event that occurs at the second act curtain triggers the end of the movie.
10. The third act must build, build, build in tempo and action until the last event, and then -- that's it. Don't hang around.