Playing your first session of Dungeons and Dragons is an exciting, but also very confusing experience. You may find that even after reading the rules a thousand times, the only way to get comfortable playing is by experiencing the game. However, it is definitely helpful to prepare before each session when you’re new, and it can help you, and your Dungeon Master, be significantly less stressed if you have everything laid out ahead of time. 

For those who play spellcasters: prepare your spells before the session begins, or you will be frantically flipping through notes and books to search for something that could have been organized before you’re two hours into a session. As well as this, keeping the spells you have prepared is very helpful to making gameplay easier on you, making sure to keep track of what level they are, and maintaining the right number of spells. 

For more combat oriented classes, you need to know all of your abilities. It’s far too easy to fall into making the same two attacks every single time you’re in combat, so knowing every single thing your character is capable of doing is important for the quality of your game. 

To review: yes, your first session will be awkward, confusing, and you won’t really know what’s going on, but preparing and knowing your character will make everything run smoothly, and will be generally easier to understand.