A monopoly can be achieved the following ways:
- Getting perfect patent coverage
- Owning land will sometimes create a local monopoly. For example a skicenter
- Being dominant in an area of business where network effect is strong and there are barriers to changing. (I thought about Facebook until Google+ came along. I do not have other good examples).
- Having an exclusive sales deal with a monopolistic producer
- Being the only provider who has been approved by an approval agency or government
Of course, as with all monopolies, if one exploits the position too much, competition will come.