Quantum numbers have to be taught, but many students just write them off as too hard from the beginning.
This worksheet is best to use at the very beginning, after you have introduced the concept of quantum numbers. Use it as classwork or homework. Students will look at the labeled diagram and answer the questions. The diagram has them look at the difference between an orbital, shell, and subshell through questions. The worksheet also asks the students to draw specified orbitals, shells, and subshells. Answers are included.
After this worksheet, I would use this one:
The second page of the worksheet is about the general shape of each type of orbital. There is usually at least one of these questions on the AP test.