Understand the significance of neurotransmitters. Studying the big picture can help you learn more about scientific concepts. Neurotransmitters are responsible for all of the signals being sent to your brain. For example, if you want to lift your pencil, impulses are sent to your brain for each movement, and neurotransmitters are responsible for passing along these impulses so that they can be translated into movements.
Go a bit deeper. After you understand the basic idea of neurotransmitters, you can start studying the subject more in depth. For example, there are different neurotransmitter types, each with a different type of function. Serotonin is just one substance that acts as a neurotransmitter. It's responsible for constricting your blood vessels.
Make flash cards. While studying neurotransmitters, you may come across a lot of terminology that sounds vague and complicated. As you learn each word, make a flash card and write the definition of the word on the back. Drawing a small diagram might also be helpful as you study.
Study the subject of neurotransmitters in small time frames, such as an hour or two. When you cram on a scientific subject and try to learn everything in one long chunk of time, then you will likely forget a lot of what you studied, especially what you studied in the middle of the session.
Ask questions. If you're learning about neurotransmitters as part of a science course you're taking, ask your instructor questions when you have them. The subject of neurotransmitters will get increasingly complicated as you go deeper, and if you don't understand something now, it could inhibit your ability to understand a more complex subject later on.