The patent practitioners in the forum should have better suggestions than I, but here are some basic points for general background and context. I'm not a patent-practitioner myself, so take what I say with a grain or two -- or even a fist-full -- of salt till the true patent people correct or confirm this, but in a mangled mix of lay terms and patent jargon, here's my version of "Patents 101":
The patent is a means to protect an invention (including processes and, I believe, certain methods).
The invention has to be more than just an inchoate idea however; you have to actually have made a workable version of the invention ("reduced it to practice") before you can patent it.
The invention must be something new ("novel").
It must be something "useful" (unless you're going for a design patent, i.e mere ornamentation, but that's another animal). It's got to be good for something.
It must be "non-obvious"--if someone who both is skilled in the art (knows this field of science) and also knows about other similar inventions that are already out there (prior art) would look at the invention and say, "so what?, anyone would know to do that!," then the gizmo might be one that's "obvious".
And the invention must not be of the sort that falls into certain statutory exclusions.
To make sure your invention is novel and non-obvious, a patent search must be done for "prior art" -- earlier inventions which have been either patented or described in scientific journals or other public literature which may be considered to have led up to or anticipated (or been the same as) your invention. If your invention is among them, it's not novel. If your invention is just the next logical step from those, then it's "obvious." Knowing what the prior art is is crucial to determining patentability, so you want the search done by someone who knows what they're doing. (Having this information also helps you craft the claims of the patent application so they cover only what's novel, useful, and non-obvious.) And note that if someone else published or patented your invention first, it doesn't matter if you came up with your idea independently. In patents, first in time is first in right.
Once you make your invention public, in the US you have just one year in which to file for a patent. I believe that, in many other countries, making the invention public automatically bars you from patenting it, so if you think you've got something with international potential--keep it secret (and use non-disclosure agreements if you need to show it to outsiders, like investors, e.g.).
In the US it is possible to stop the clock on the one-year deadline (at least for a time) by filing a "provisional" patent application. My understanding is that this involves gathering together all your notebooks on the invention, showing everything that will be needed to properly describe the invention (including notes on its reduction to practice?), and filing the lot with the PTO. Then you and your attorney can take more time to sort it all out into proper claims in a regular application, which gets a priority date going back to when you filed the provisional application.
Critical to protecting your invention with a patent are the claims. The proper drafting of claims is a highly specialized art which, to be done right, requires both knowledge of the patent law and of the science involved. The claims effectively are the patent. (The drafting of the specification of the patent is also important, since that can influence how the claims are interpreted.) The claims describe what is protected. Mess up a claim, and your patent, even if granted, may protect the wrong thing and be worthless to you. This is a good reason, if you can afford it, to have the patent application drawn up by a patent attorney or patent agent.
A decent website with patent basics is:
http://www.bitlaw.com/patent/requirements.htmlNolo press books are pretty good in translating law into lay terms. The one on filing your own patents is shown at:
http://www.nolo.com/products/patent-it-yourself-PAT.html (It has a section on determining whether or not your idea is patentable.)