Depending on which hot spot you are using, you are most likely to pay a fee ranging from a per hour basis to a subscribtion for a week or month. However, other hotspots require you to enter further details, say for example if you are part of a phone network that has hotspots available (Telstra, for example, has thousands of hotspots open for people who use the Telstra network) or hotels who require you to enter a room name and predesignated password which will be supplied if you are staying there.
Then there are the small portion of hotspots that are totally free, ranging from McDonald's to the Coffee Club to many other free hotspots which are provided to either increase popularity of an establishment, or provide free internet access to people in a certain area.
Depends on the place. Some are absolutely free but others have agreements with providers.. If its at&t you need to already have internet with them. If its t-mobile you need a cell phone plan and an extra $5 a month