Make sure you get enough sleep. It often seems like such a good idea to have late nights, finishing off work or just hanging out. But sleep plays a crucial role in declarative memory by processing and consolidating newly acquired information.
Check out this article: More Evidence That Sleep Enhances Memory and Learning.
Meditation has also been proven to decrease stress and improve memory and learning. Read this great article:
Proof that Meditation CAN Grow Your Brain.
Try the free Headspace 10-day Challenge and watch your stress decrease and your focus increase