First of all, welcome to EMTLife!
The advice I give to anyone preparing for the ACP exam is to study the AOCP very thoroughly. If your instructor hasn't already talked to you about it you can find it on the ACP website. Expect the same type of questions that were on the EMR exam, the questions will be similar in nature, but to a higher level and will expect a higher standard of critical thinking. They often put obscure things on the exam such as APGAR scores and Cushing's triad.
Don't wait till the week before to study, continuously review from the time you're finished class to the exam. Doesn't sound like that's an issue if your platoon is starting already!
Read the whole question, underline the important bits. Don't over-think the question. If you're stuck, move on and come back to it later so you don't waste time. There will likely be something later on in the exam that may help you answer the question. If you're still stuck use the process of elimination, but remember to keep it simple.
Secondly, I suggest making sure that you are very well practiced in verbalizing everything in both the medical and the trauma scenarios. Look over the exam policies and be sure you stay within your scope; there have been a lot of failures lately for out of scope procedures. Your preceptors might help you out by running through some typical ACP style scenarios between calls.
The day before the exam, DO NOT do a hardcore day of cramming, this will stress you out more. All of your studying should be done well before now! If you need, look over your material a few times throughout the day, but try to relax the day before so you don't psych yourself out. Focus on you the day before; eat well, hydrate yourself and try to avoid caffeine or stimulants. Get a good night's sleep. (Trust me, getting a good night's sleep is crucial.)
The day of the exam, eat a proper breakfast and lunch. Allow yourself plenty of time to get to the exam, don't add to the stress by being late.
Lastly,
GOOD LUCK!