There is a one year clock on a provisional patent after which you must have filed for a normal patent. The material you file for a provisional patent needs to

There is a one year clock on a provisional patent after which you must have filed for a normal patent. The material you file for a provisional patent needs to fully disclose your invention and provide "support" for any claims that you make or will make. You do not need to file claims with a provisional patent. You may find that writing claims will help you determine whether you have fully disclosed your invention and identified all the limitations. You should do a prior art search before filing the provisional so that you understand where your invention falls in the sea of other patented inventions. No sense trying to patent an "invention" which is not patentable over the prior art. You can cut costs by doing the paperwork yourself, but before you file it is usually worthwhile to have the materials looked over by a patent attorney. I am not a patent attorney but I have had some experience with patents.