OK,  How do you size a snowboard,  how do I know which size snowboard I should ride? which size board is right for me?  I hear you can learn snowboarding so fast theres no reason to get a beginner board since you'll just outgrow it.  All common questions we get quite a bit here at 720Sports,   I know most of you are under the belief that the length of the board should come between your chin and nose,   In the early days of snowboarding this was a fairly effective way of sizing a board so long as the person was of average weight for that height.    Here in 2007/2008 that still works BUT there are much better deciding factors.   In the interest of keeping this a very simple and basic guide I will not be addressing complicating factors such as board effective edge and torsional stiffness as it relates to board sizing. 

Weight is a more accurate indicator of which size board is appropriate for you,  think about it-  If you are 5 feet tall and weigh 300Lbs  you need more flotation (IE a longer snowboard) than someone who is 6.2 but only weighs 150.  So weight is a good starting place....

However weight alone is not the ultimate deciding factor,  if you are on the east coast riding hardpack and ice is a 15 lb over or under the recommended manufacturer weight  difference really going to affect your riding?   Size is an extremely personal preference, I weigh 175 lbs,  I ride everything from  a 172 powder deck to a 152 twin,  it simply depends on where and what conditions I plan on riding that day.   Don't get locked into the thought process that you ride a 155 and thats the only size you fit.   a 2-3 CM difference either longer or shorter is going to be very difficult to even notice for most riders,  Instead think more in terms about what you like to ride, 

           1) Are you into the park and pipe?  Trying to nail down that 360 or 540?  Then a shorter board may be what you are looking for- something that spins and turns extremely quickly. 

           2) Are you a Tree Monkey?   Then you may want something in a mid length-  you need to be able to cut the board over quickly to avoid those trees (they're made out of wood you know:)  but if its too short and you get into a powder stash in the trees you'll be miserable really quick. 

          3) Do you simply like to rip down the hill at mach 2?  Then a longer board will  be a fast and stable platform for a human missile

          4) Powder hound?  Wide nose, Narrow tail and extra length will have you surfing the mountain

Some (Very) General Board Rules:

• Shorter boards turn quicker and spin easier - However they are a bit squirrelly at speed and don't float in powder
• A longer Board is Faster and More stable at speed- But it won't turn as fast and you better clear the tip/tail off the ground in a spin
• Wide Boards float better in deep powder and keep big foots from dragging their toes- But they are harder to turn and do not handle as well as a narrow board (but if your a sz 12 then this is your deck)
• Twin Tips- Great for riding switch, spinning and landing switch- awesome on the groomers,  More drag from the twin shape so not so great in backcountry or in powder
• Hi end advanced stiffer flex boards are faster and handle big ugly landings better- True But they are also harder to work and turn and they are exceedingly unforgiving of rider mistakes, In other words they will smash  you into the ground in a heartbeat 
• lower model softer flex boards are better for beginners and jibbing you'll learn faster and progress quicker with less chance of injury.  But once you get comfortable at speed and turns you'll want something a bit stiffer to rip on:)

I hope this guide was somewhat helpful and didn't serve to confuse you even more,  but there simply is no precise exact down to the centimeter size you should be riding... Its all about what you like, enjoy and most importantly have fun on, After all- thats why we snowboard to begin with:)