There are actually several types of skateboards but the most common ones are the longboard, cruiser, and carve skateboards. A longboard is usually at least 33 inches. It is a great mode of transportation and works well for cruising around. The cruiser also works well as a mode of transportation but many consider it more beneficial as it has a shorter skateboard, which promotes ease in transporting around.
Many of the most popular skateboard brands sponsor teams of skaters, like Zero's Jamie Thomas and Element's Barn Margera. Professional skaters are often good sources of information as to what skateboard you should buy. If a pro skater rides a certain board, there is a good chance that if he or she finds that it is high enough quality you will also like the board. Users looking for a new skateboard will want to research a variety of different brands to find the one that best suits their needs, based on function and features.
You can get a lot of advice (and maybe too many opinions) from fellow skaters. Some of it might not be as informed or educated as a shop owner's (and some might be flat-out bad advice), but it should at least be sincere! If you don't have a local skate park, or are too uncomfortable to walk up to people and ask, you can also ask around on a skateboarding forum. People there will be more than happy to tell you what they think about deck brands.