In LA or the mountains?
If you are visiting for a short time and want to go with a shop, research the ones near your destination, call ahead & see if they have consignment deals, last year's models, etc. They are eager to sell this year because they know rentals will be down due to the economy. Craigslist is a great source, too. Find what you want, call ahead, & meet the seller near the resort. As for the model, no advice there, everyone has there own style. I've had Burtons, Rides, Unity (Dominion 169 could be the best powder board ever!), Capita(Austrian), all sweet. People love to rag Burton, but I've got two, and cannot destroy them. My ten year old Floater is still ready to dominate Wolfie powder, just doesn't look all cool & stylie.
A good warehouse online source is H-house, great package deals, and you get some sweet goggles or shades w/ board purchase.
Check the construction & materials. Expensive boards use expensive stuff, but go faster w/ sintered base, stomp landings & carve sweet from progressive flexy stuff, awesome responsiveness from higher end rails, and hold up better over time. Good Luck