Learning to snowboard is such a great idea -- it make winter much more tolerable. There's a great guide here about picking a board: http://www.overstock.com/Heaven-is-a-Halfpipe/2243/blogpost

The length of your snowboard depends a lot on weight. If you are just starting out, get a cheap all mountain snowboard, but splurge on your boots and bindings. Once you figure what you are doing, and what you like and don't like about your board, then get yourself a nice board.

Very easy hold the board up to your face it should reach between your nose and chin ideally being on your lips.