First off, you should attend class as often as you possibly can. This is where you will learn the techniques that you will need to know to test for your next belt. You will also get advice and feedback from your instructors that will help you to improve your technique.
You will learn a Songahm Taekwondo form that you must memorize and be able to perform at the promotional event. These are preplanned moves that teach you proper technique and execution, build strength and coordination and help you to visualize using these techniques in a real life situation. The Songahm form may be 18 moves up to 46 moves long, depending upon your rank and the particular form that you are learning.
At the ranks of White, Orange and Yellow, you will also learn and demonstrate one-step sparring techniques. This is a set of sparring moves designed to teach you to interact with other people.
At Camouflage belt rank through Green belt rank you will learn and demonstrate several sparring flows. You also begin to free spar with other people at the rank of 4th grade Camouflage belt. This continues through the rest of your training.
At the rank of 6th grade purple belt, you will break boards as part of your promotion to your next rank.
At the rank of 1st degree Black Belt, you must now spar 2 rounds at your testing event. It also now becomes a true test of your abilities, with the very real possibility of not changing in rank. We like to tell people that this "no-change" is not a failure, but an indicator of needing to continue working and preparing to achieve your goal.
Remember that your instructors are watching you and evaluating you in every class. This is where the true test of your abilities is done. Trust in what they tell you, and follow their advice and you will go a long way on your quest to achieve the Black Belt rank.