We are a group of researchers in Europe, interested in filling a provisional application for a patent regarding a device that we developed.
What is the cheapest, fastest and more effective way to do this?
Cheapest is to write as complete a description as you can, include drawings that the text makes reference to and then fill out a provisional application cover sheet. Either mail it all to the USPTO or file it electronically using EFS-Web I suppose the fastest is to do the above but use whatever description you already have created - maybe a PowerPoint presentation. Of course these approaches may not be the most effective.
To be most effective I would definitely get advice from a US registered patent practitioner. Although it is said that provisional applications have few formal requiremnts, if it ever actually comes into play as something you are relying upon, the sufficiency of its content will be judged under 35 USC section 112, exactly by the same criteria the content of a "regular" patent is judged.
Having it drafted and filed by a professional is highly recommended.(yes, I am one) Someone that works as a solo practitioner or in a small practice might be more oriented to cost-sensitive inventors.
If your only goal is to obtain a (so-called) priority date which can be used to claim priority from in later patent applications (to be filed directly in any country where protection is needed, or indirectly, via the PCT system) then you can even file a patent application without payment of any official fees. Such a filing can be achieved at the European Patent Office, and many of the national patent offices in European countries. Filing of such an application can be done by anyone.
However, for such a filing to be effective, i.e. to provide sufficient basis for a later priority claim, should still be as complete as possible and certainly should provide all information that a skilled person would need to repeat the invention (i.e. it should fulfill the enablement requirement). Since drafting of patent applications is difficult and should be done with the utmost care - also the drafting of such a 'provisional application'- it is strongly adviced to seek the help or advice of a patent agent or patent attorney.
George White makes excellent points.
I would like to add that in between the gold standard (and almost necessary to filing a good provisional application) of consulting a professional, and the sub-standard of doing it completely by yourself with no understanding of the intricacies of patent practice is the option of a 'pseudo-guided provisional' such as IP Watchdog's invent+patent system (there are other ones, and I have no relation or association to any of them).
No, it is NOT the same as having a patent practitioner draft it (yes, I am one). Yes, it is far better than trying to do it yourself, as it is designed (a good one at least) by someone who understands the intricacies of patent practice to draw out as much information as possible and get it into the provisional application to later support a strong non-provisional application (drafted by a skilled practitioner). Without having actually used the Invent+Patent system, but having reviewed as much as possible about it, it seems like an excellent compromise for an absolutely cash-strapped inventor. Furthermore, the cost should not be an issue if you have enough cash to file the provisional.
Another tip: When drafting an application, include LOTS of examples (even sub-standard ones, but especially all conceivable variations of 'good' ones). Include LOTS of tables with different ranges of various parameters - possible ranges, ideal ranges, preferred ranges. Examples of environments, scenarios, configurations. Everything you can think of. It will help a strong application to be drafted later that can point back to details in your provisional to avoid your filing date being rejected because of new matter.