What's the best way....

[daBigNY]

...to build japanese vocabulary? is there software, book or other thing that one may suggest?

 

[Scrivener]

You can't get far learning vocab without learning kanji, so learn them together if possible.

But grammar is more important than vocab IMHO.

 

[Buntaro]

The first step is to get through a Japanese textbook cover to cover. Then, start writing letters and stories. Get a pen-pal, or another Japanese-language student and write letters and notes to each other.

 

[Emoni]

Depends on your level, for the most part just start with college level text books, then grab a dictionary and look up words that you hear or read.

 

[Fantt]

I bought a used copy of .Nakama 1. In the first chapter it has more than 50 vocabulary words. I'm creating note cards to help me learn the words.

Pimsleur is also helping with my vocabulary, as is Instant Immersion Japanese which I picked up at CostCo for $16. It's pretty danged awesome at that price, by the way.

I would reccomend a text book as well for picking up grammar along with your words.