Check out these must have mappings for working with JSON in Vim:
ajprovides a text object for the outermost JSON object, array, string, number, or keyword.
gqaj"pretty prints" (wraps/indents/sorts keys/otherwise cleans up) the JSON construct under the cursor.
gwajtakes the JSON object on the clipboard and extends it into the JSON object under the cursor.
There are also
ij variants that target innermost rather than outermost JSON
If you don't have a preferred installation method, I recommend installing pathogen.vim, and then simply copy and paste:
cd ~/.vim/bundle git clone git://github.com/tpope/vim-jdaddy.git
Copyright © Tim Pope. Distributed under the same terms as Vim itself.