Looks aren't everything, and while certain boards may catch your eye in the surf shop, remember that it's always better to look good surfing on a simple board, then surf terribly on a cool one. Here's why it's important.
Different boards require different skills.
If the board is very small, narrow, and pointy, it's going to be very squirrely underfoot. Good if you are a professional-level surfer in a huge wave, but very bad if you are just starting out. If you get a bigger board, you will have an easier time.
Surfboards are shaped differently for different waves.
Not all waves are shaped the same. Some are huge, some are tiny and gentle, and thousands in between. If you live where the waves are small and weak and you get a board with very little buoyancy (cubic liters of volume), you aren't going to catch very many waves. Likewise, if you buy a 9ft longboard and try paddling out into huge, steep waves, this will also wreck your fun time. So choose a board that's appropriate for your local beach.
Don't take the guy at the shop's advice.
People who work at surfboard shops aren't coaches, and often they are not the brightest advice givers. They are trying to sell surfboards. Often they are trying to sell the boards that they want to ride, which may be a totally different skill level than you. Nothing is worse than dropping $800 on a board that is too difficult to ride and letting it sit in the garage to die.
conclusion.
Do your research and pick a board from a reputable manufacturer. Look at the size and weight charts. If you are a beginner or your weight changes often, bigger is better, and remember that the board looks pretty in the shop but you will be covering it in ugly, bumpy surf wax and holding it underwater most of the time : )
