How to do a patent search

http://www.inventions-handbook.com/patent-search-online.html
How to do a patent search
You have an invention idea, so now it’s the time to do some preliminary research to see if it is new and what else exists in the market.
Using your initial ideas, start looking for what the market has to offer. Google the description of your new product, questions regarding the need and even sentences you think are relevant.
You are trying to find out not only what products already exist in the market, but also if there is a real need for your invention idea. Will people be interested in such an invention?
These sort of searches will bring relevant posts and questions in forums and communities and will give you an idea of the needs and problems relevant to your invention concept.
You might also see other posters recommending appropriate solutions - these are potential competitors for your invention idea.
Remember, the objective of an invention research is to find out not only if a similar product exists in the market, but also if there is a commercial potential to your invention.
This is by no means enough to gauge if people might pay for your invention, you still need to do a more thorough analysis, but it will give you an idea of how critical is the need and if the solutions offered in the market are good enough or not.
If your invention idea did come up in your research, you probably cannot patent it. Try to find a new improvement on the existing products or another idea to help solve any perceivable problems with existing products.
Nothing similar comes up? Good, you might be on to something. However, in this case it’s even more important to try and research the need.
If nothing similar exists, you need to question whether you are really solving a real problem. If you are, then you are definitely on the right path. Lets move to the next step in the 'how to patent an invention' process.
Once you established through your invention research that your invention idea doesn’t exist, it’s time to check if it has been patented before.
Did you manage to find something similar to your invention in the patent database? Always conduct several searches and use your invention notebook from step two to make sure you cover all the relevant keywords and potential classifications.
If nothing similar comes up - great. If some patents remind you of your invention idea but are not quite the same, print their documents and save them. They will be useful once you do approach a patent attorney to investigate patenting your invention.