Well, this worked out for me so I figure I'll share what helped. I searched in vain for some good advice before taking the SIFT myself, so maybe this will help someone else out.
First, download the SIFT FAQ from the USAREC WO Recruiting website.
Take a look at all of the different subtests.
Go to http://www.usarec.army.mil/hq/...d/militaryflight.pdf
and download the PDF.
Every subtest on the SIFT (except for the Army Aviation Information Test) can be found in the military flight study guide from the link above. Most of them come from different branch study guides but the material is the same.
For the Army Aviation Information Test your best resource is the FAA Rotorcraft Flying Handbook that can be found here http://www.faa.gov/regulations...ia/faa-h-8083-21.pdf
What I did was print out each subtest study guide and practice tests and created a study binder.
I didn't spend a whole lot of time studying the FAA Handbook and I'm sure I bombed that part of the test but I still made out with a 62 on the SIFT, which was good enough to get me Selected for 153A during the May 2013 board.
My best advice is don't overthink it, schedule the test when you are comfortable taking it. I didn't study much at all, maybe 10 hours total in the 2 weeks before I took the test. I don't have any background knowledge of helicopters or aviation. I have an Infantry background.
In my opinion the worst thing you can do is never take the test because you are worried you won't pass it. Definitely take it seriously and study as much as you deem necessary, but don't sideline your goals because you are nervous about the test.