Recently bought new bike gears keep slipping

hosso1986 Posts: 2
edited September 2009 in MTB beginners
Have just completed first week of riding a specialized hardrock i picked up new last weekend and found that my rear gears keep slipping. Anyone advise of a decent video to watch to learn how to tighten to resolve this issue or advise that you can give. Only just recently picked up a bike since about the age of 15 so any help much appreciated.