What is the best way to gather information to know what a client is looking for on their website?
What sorts of things do you mean? Obviously talking with them is helpful. 
It’s amazing how often this doesn’t happen, though. Sometimes, if there’s a series of people outsourcing parts of a site one to another (and you are the one down the line), you almost need a ouija board to work out what the client wants, which is a hopeless situation.