The test has 3 parts as you may already know and here is how I looked at it.

General-Has 150 questions and you are allowed to miss 42 and still pass.
Are you taking the class too? Because in the class they give you about 300 practice question to see what its like. don't worry about time they give you 2 hours and it was more then enough for me and others. Just put check marks next to the questions you are not sure about and come back at the end and make sure you don't have more then 42 check marks. A lot of the questions have two question like;
answer D. (A and B)
answer E. (B and C)
Most of the time B will be one of the answers now all you need to do is look at (A and C) but on the other hand if B is not one of the answers then you have just eliminated answers D. and E and B now the answers is either A or C. I only did this with questions I didn't know the answers too and I guess it worked.

Open Book-If you are taking API 1104 don't lose any sleep on the open book. There are 46 questions and you can miss 13 and still pass. And the book is only 70 pages and you only use about 37 pages. So with this you can look up all 46 questions if you have your book tabbed and know your accept or reject area.
Now if you are taking AWS D1.1 the so called mans code, then God bless you and your going to lose some sleep. All I can say is know your book and tab the hell out of it.

Hands On-Here is where you might have trouble if you say you don't have background in NDT testing. I am a level 2 radiographer so this section was a little easy until they give you a made up code book to test by. They send you this book before they exam so you can get a heads up on it. You have to know how to use their tools and the only one I found to be very useful was the 6 inch steel ruler. Measure everything in 64th. The porosity samples they gave us had holes drilled in them but were all the same size, so if you measure one and multiply its easy. They give you some pictures to look at and tell what they show. Know the difference between a Yoke and Prod that can be a tricky one. One picture had the guy doing Dye penetrate wrong so know the steps in that and technique. They give you all the conversions so you just fill in and multiply.

You will be nervous because of how much it cost and just the thought of taking a serious test. But there are 2 hours to each section and it is an enough time if you are OK with everything.
Good luck and let me know how you do. Feel free to ask any specific questions.