The test consists of math & reading concepts. As far as the math goes, you'll be tested on adding, subtracting, multiplying, dividing......both whole numbers & fractions. If you haven't dealt with fractions in awhile, then I would advise familiarizing yourself with them as there are many questions dealing with fractions. There are also a few algebra questions, but nothing too difficult. I was not allowed to use a calculator, but I have heard other people claim that they were able to use one. Find out whether your school allows it or not.
The reading comprehension is based on how long it takes you to read the paragraphs & also finish the questions that are asked regarding the content of what you just read.
I went into the test without studying (because I had no idea what to expect either) & scored 89%. I didn't find it to be a difficult exam. The one thing I didn't like about it is that it's computerized (at least at my school it was), so once you answer a question, you cannot go back & change it. I know there is a study guide out there for this test that costs around $34. I was advised that it wasn't worth the money, but it's your choice if you feel the need to see exactly what to expect on the exam.
I was not able to find any web sites with anything informational regarding the NET. That was last year though, perhaps there might be something out there now.
Good luck to you!!