A prior art search is done to ensure that you have a patentable invention before you get too involved in the process.
Title searches and searching all fields are NOT the way to go with these searches because the words used to describe a patent are very general and these documents are full of legal jargon.
You will instead want to do an advanced search using the patent classes under which your invention might be listed and searching primarily in certain sections of the patent applications to catch the most relevant existent matches.
In 2013, the USPTO switched to using an international system of patent classification called the Cooperative Patent Classification System. Some patents which are older will still have the outdated United States Patent Classification (USPC) system codes attached to them and these will also be useful to use during your search process.
1. Go to freepatentsonline.com
2. Click "Search".
3. Click "Expert Search".
4. To begin we will cast a very wide net and ty to find all the things which could be related to your idea. We will search in the claims and abstracts of all the patents and patent applications. (Click this link for a step by step instructions for formatting your search.)
5. Perform a first round search: Put the query formed in step 4 into the search box. Be sure that you have selected the boxes at the right hand side of the screen to search in "US Patents" and "US patent applications" as well as searching in "all years". 
6. Here is a spreadsheet to help you record your results. Please start by making a copy of this form to keep for yourself so you can track your own results. Record the search you used in column A.
7. Examine your results from the first round searches to determine which results are actually near matches to your idea. Make a list of all the patents and applications that may be near matches in column B.
8. Now you will need to open the file for each of these possible near matches (using the option to "open in new tab" will make this much easier so you don't need to go back so many steps for each new one you look at.)
9. Use the information you have gathered to this point to write some additional search queries. This time you will be limiting your search to the relevant classes. Begin each of these searches with "IPC/" followed by one of the international class codes which you found in the pervious searches or with "CCL/" for the US class codes. Then add on only one of your key search terms at a time. (Click here for more detailed instructions on writing this type of query.)
10. Perform these new searches and record your results on your spreadsheet as you did in steps 7-8.
11. Repeat all the above steps making changes to your search queries until you stop getting new novel results or until you feel you have exhausted all the search terms that are relevant to your project.
12. Once you have all the results you feel are relevant recorded in this spreadsheet, take all the patent numbers you have found thus far (recorded in column E) and copy them into column A. Return to the beginning search page by clicking "search" at the top of the page. Now we are going to dig deeper into the records of the patents which appear relevant to your project. This time around you can just enter the patent numbers into the search box (one at a time, repeating this step for each one.) If any of these appear to be relevant record the information about them in that line of your spreadsheet, if not just use the strikethrough font on that line and move on. Examine these to see if there are any new related classes here which you have not already searched in, there are record those when this step is finished return to step 9.
13. This process will likely take several iterations to ensure you have used all the possible synonyms searched within all the relevant classes. Continue refining your search query and running through these steps as many times as needed until you feel you have exhausted the possibilities and and have thorough list of near matches.
