Just to help out I can describe how a movement I was involved in worked, it might help you out. It started with a letter to the Irish Times, a facebook page and a website. The idea was spread as much as possible mostly using social media, its the most efficient and is free!
Once there is an expression of interest from enough people a meeting was organised, a room in a hotel. Attendees chipped in for the cost of the room. Get a facilitator (there are lots of them they work with organisations) maybe one of your interested people is one and would volunteer to do it. Spend the day working on a document something to start off with, it should be broad to include as many people as possible. Use the skills of those there maybe there is a journalist, a writer, academics etc who can help. Write up a document with sections such as an introduction, aims, values etc whatever is appropriate but not too long.
Try and have chapters in different parts of the country who can meet and discuss tactics. A movement needs money for fliers etc so you'd need to figure out how to raise some, maybe a benefactor, I bet there are a lot of libertarians in the US who might sponsor you, otherwise ask for donations or have a membership fee.
By then you should have an idea of how many people are interested, try and get into the media and involved in the issues of the day giving an opinion.
Where it goes from there depends on how successful you are but its a starting point.
It is alot of work but from my experience it gets the ball rolling. People will be really enthusiastic for a while then drop off. So long as someone is keeping it moving forward though thats a positive thing.