Tech Radar have put together a very useful and well-written article on the setting up and running of a LUG. It is, at first glance, UK-centric but the ideas in their should translate to any country.
It also mentions using social networking sites to publicise events. Have a read is you are looking to set up a LUG and definitely have a read if you tink your current LUGs membership may be stagnating.
Article is here