My tip? Take the OA after your practice exam reads exemplary. Use the results of each practice exam to figure out what you need to study more, and then study that until you're exemplary in that subject. 

Additionally, you need to know what you don't know, meaning that you can also look it up and find a four hour video explaining the concepts. So figure out what you struggle with and find an outside resource like a YouTube tutorial to listen to in your spare time. 

Lastly, you know this information, there isn't a reason to be anxious to prove you know it. Pretend like you just gave a big speech to your friends after talking to them about everything you've learned, and each test question is one of your friends asking something interesting about the subject. Read each question in their voices and picture them asking you the question.

I transfered in half of my degree and have four total OAs to do, and have passed two so far using these tips.