Using the wait list is an excellent strategy to improve your schedule. It might help you get the classes that you want or need.
If a class you want to take is filled, you can join a wait list on CUNYfirst. Make sure to do your class search with the Show Open Classes Only box unchecked. The classes with a wait list have a yellow triangle icon toward the right-hand side.
However, there is always the chance that your schedule will stay the same if other students don’t drop your desired class. It’s always good to have a “Plan B” in mind.