Getting enough sleep is necessary for our memory. Especially getting in REM sleep which comes later on during your all-night sleep. This is why you should ideally get in at least 6 hours of sleep per night. It has been proven that during REM sleeps the things you have learned are being stored ad memorized.
Learn to relax
Being able to relax is a very good skill to have. When you are under stress and you can't relax and take a break you will have trouble focusing. When you have a problem focusing, your memory will be foggy.
Practice often, in small parts and test yourself. By spacing out your practice the information will really "get under your skin" and there is a high chance you will remember it for much longer.
Creating a mind map when studying is a very good way to remember information. It helps you to make connections and see things in a bigger picture.
Eating well will help you to be more aware and much more focused. You will feel fresh and more awake. Good nutrition will make you feel better and therefore even your memory will be better. Eat better, live better.