I took my exam in October and scored a 95 on it. 100 on math, 88 on grammar, 98 on reading comprehension, and 94 on vocab and general knowledge. I did not have to take any science exams but I can offer some advise on the ones I did take.
I purchased the study guide Hesi A2 Secrets by Mometrix Media LCC and studied it semi-regularly before my exam. The vocabulary was the most useful part of this guide (it includes about 300 commonly used words on the exams). I was questioned on many of these words so this guide was my saving grace.
For the math portion make sure you fully understand proportions and how to solve them. Probably 25% of my math questions were simple proportions. Another large component was conversions. Metric to metric mostly, with a few metric to US mass. Also, make sure you read the questions and know what it is asking. Quite a few of my problems had unnecessary information that could be misleading.
I would also suggest brushing up on all the grammar rules. As you can see, I did the worst in this area. While taking the test I thought the answers were so simple and straightforward so I zoomed right through it. In retrospect, I would go slower and make sure my answers followed all of the rules.
Lastly, and maybe most importantly, just breathe! I was very nervous when I took my exam and had a million butterflies. I needed to get a 93 or above on mine and had no idea what to expect. I took my time answering all of the questions (except for in my first section, grammar). You have plenty of time so double check your answers before you submit. Get a study guide (or borrow one from the library) and read a little each night and you'll do great.