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.
Without good grip tape, skaters have a tough time staying on top of their board. The main complaints about poor grip tape tend to be that it was never very grippy or lost its grip really quickly. Once again, we recommend trusting in name brands with years of experience supporting skateboarders. Unfortunately, if you are buying a pre-made complete skateboard, you probably won't have access to the brand name of the grip.