what to look for when buying or renting a snowboard...

what should i look for? do i want a stiff board or a flexible one? should i look for thickness and length? material its made of? or brand?
http://cosprings.craigslist.org/spo/249939173.html
how does that look?
http://cosprings.craigslist.org/spo/249939173.html
how does that look?