How to do an effective patent search?

[bcnu]

Just looking at patents is a start, but is only the tip of the proverbial ice burg. To be patentable, it has to be "new and non-obvious" when compared against any patent ever granted anywhere in the world, any patent application ever filed (and published) and any other publication in any language anywhere in the world, not to mention any other device or process ever used in public, or their equivalents, or any obvious combinations or improvements of any of the above.

You cannot do a "patentability search" without professional guidance.

@StephenWeinstein's ideas are valuable, but failed to mention that you cannot search any US patents on the USPTO database prior to about 1983 (only by serial number), but the google.com/patents has a much better inventory, as do other patent search engines. Again, this has VERY LITTLE to do with whether something is patentable, since the vast majority of existing inventions are NOT patented, yet their existence or prior disclosure prevent anyone else from ever patenting anything similar.