Generally, when people talk about choosing keywords for a website, what they're really talking about is choosing keyword phrases. With a few exceptions, singular keywords are just too general. They're either not going to be precise enough to get any traction, or they're going to be so over-used that it's impossible to rank for them. For instance, using just the name of the city doesn't go far enough, as people are generally going to search for what they want to find in that city, not just the name itself. Something else like the word "shoes" is going to be saturated and won't really help, even if you do sell shoes.
