Knowing how to use transitions come in handy when you're editing video. Transitions have many uses, from making two different images flow together, to giving your viewer subtle clues as to the progression of your story. A fade to black/fade from black can represent the end of a scene, and the beginning of a new day. A cross dissolve can be used to give your video a relaxed pace. That being said, FCP 7 includes plenty of silly transitions such as spins and stretches to let you express a light-hearted point of view.
To access the video transitions menu, go to Effects > Video Transitions. This will lead you to a drop-down menu of transition options.