I took LPN boards last July. I did my studying out of the NCLEX-PN Review book by Saunders. I worked through the whole book over the course of 6 or so weeks, doing some questions almost every day.
I felt horrible coming out of the test; it cut me off at the minimum number of questions (75 or 85, I can't remember). A couple days of sitting on pins and needles, and then the joy of finding out I passed!
Now I have to study for the RN NCLEX.....
Just carve out some regular time to study and you should be fine. Getting a good night's sleep and going in with a positive attitude (don't doubt yourself, you probably know more than you think you do!) will help tremendously.
Best of luck to you!