First of all lets clairify what a provisional patent is... It's not a patent and does not hold the same teeth as a patent does. Simply put, it gives you the right to put Patent Pending on some technology that you are developing. In addition, if you apply for a patent in a years time from time of the filing of the provisional patent, the effective date of the patent (assuming it's approved... not all patents are) is the date of provisional patent filing. Oh, the date of provisional patent filing is the date you drop it off at the post office and send it via registered mail.
So, today you could write up a provisional patent document (not as formal as an actual patent application but it helps to keep it formal if you are going after the patent), enclose a check for $100.00 if you are an individual, send it via registered mail (not fedex, ups, but usps) and BAM, Patent Pending.
It doesn't mean you are going to get the patent. It's meant for smaller inventors to potentially apply for patents and decide if they want to invest the $10,000 it typically takes to possibly get a patent. The gives you protection of prior art no matter what so some company can't patent the technology even if you decide not to pursue a patent (as the provisional patent application counts as prior art and assuming the technology is "new and novel"). If you do decide to pursue a patent the effective date of the patent is the date you sent it via registered mail.