There are two ways that you can file a patent application. The provisional application is optional and buys you time before you have to file the complete or final application, which is the one you have to do before a patent will be granted.
You cannot secure your claims to a patent by simply mailing yourself your idea, having had it notarized and dated by an official perhaps or with the postmark confirming your date of mailing.
This may be 'proof' of a date, if this ever becomes contested, but it is quite a common fallacy that doing this gives you protection.
You definitely cannot patent an invention in this way. Only the State can grant a patent and therefore you have to follow the statutory channels.
Note the Steps in Patenting: How to Get a Patent before filing your patent application.
You now need to decide whether you first want to:
Eventually, before you can get a patent, you will have to file a complete (final) application to secure your patent rights - and you may want to proceed to that step right away.
However, the advantages of a provisional application are:
You've done your patent search, you've filed the provisional, and it's all systems go. By now you should know the potential and viability of your invention and you have to decide in which countries you want to apply to get a patent.
The final step for you to patent an invention is to file the Complete Patent Application within a year of the provisional application. This is a very important document.
Competent patent law firms normally have technical experts in many fields to help compile the specification and claims. You would be wise to consult with a qualified patent lawyer, because how the patent documentation is drafted is very specialized and a lot can go wrong.
You may wish to patent your invention internationally. Find out more about a PCT application and the patent prosecution - the final step in the patenting process.
You can find links to the patent offices in various countries on our Intellectual Property Resources page.
A patent application needs to make your invention and claims very clear to be considered for a patent.
Review existing patents to give you an indication of what is required, and to decide whether you need professional help.
You can prepare your own documentation, and - although generally the complete specification must be signed by a patent lawyer or agent - even do the filing yourself. It will save you quite a bit in legal fees.
However, in the long run the money spent consulting with a patent attorney to prepare your patent application is well worth it. The best thing to do is check with the lawyer on his charges for preparing and filing the relevant documentation.
The choice is yours!