Well...
I started studying for the JLPT test June 2009, but before that I had been studying Japanese by myself 8 years and in college for 3 years.
At first I wasn't sure what level I was, but after taking a few past test I guessed I might be somewhere between level 3 and 2. I spent June and half of July reviewing all of the JLPT4 vocab, and then I spent the remaining half of July and August reviewing all of the JLPT3 vocab...
I thought I might try to review all of the JLPT2 vocab too, but it started to pointless because so many of the words were Kanji compounds of kanji I already knew. I also took a few past tests of JLPT1 and JLPT2 to gage where I was (as it was apparent to me by then that I was not between JLPT2 and JLPT3) and realized that I was already scoring passing grades for JLPT2, and about 50% for JLPT1.
Figuring that I might have a shot at JLPT1 (and since I had no motivation to study for a test I was already passing) I took every single past JLPT 1 since 2008 and worked on 4 different kinds of workbooks.
I'm guessing about 300/400. The test was easier than I thought... The vocab was surprisingly a lot of the words I studied, the listening was way shorter and easier than earlier years, and the reading was pretty dull stuff but I guess I've seen worse...
But we won't know for sure until March...
Edited: 2010-01-17, 1:30 am