To shape up is to improve or develop. If your boss tells you to "shape up or ship out," you better get your act together or you may end up unemployed.
When you serve on a jury, the job is quicker if the trial shapes up to be fairly simple and straightforward. And, when winter brings more snow than usual, the spring will shape up to be especially muddy. You can also use this verb phrase to mean "get physically fit" or "improve behavior." This last meaning is an informal one, and you might hear a parent admonishing their kid: "You'd better shape up, or no ice cream tonight!"