Dealing with Similar Patents

What are some guidelines or tests I can use to figure out if I have a chance at getting patent for an idea when there are similar, but not identical, patents out there?

I don't know how to best phrase this question without actually going into the details of what I would like to patent, but I thought I give it a shot. In essence, there are two similar patents to a patent I would like to secure. One of them use a different process to get a similar result on a different interface and the other is basically a simpler version of the technology I'd like to create. I would in essence have to create a similar version of the second patent's technology and then continue it to expand it into what I would like to use it for.

For every idea that everyone has, there are similar patents out there. There are now 8 million US patents.

Generally, don't look at existing patents before trying to get your own. If you think your invention is new and valuable, then just go ahead and file. The cost of reviewing relevant prior art is not much less than the cost of filing a patent application. Of course, now that you know of these other patents, you need to tell the patent office about them when you file your application.

In terms of the test you are asking about... Your invention is patentable over these existing patents if your invention is different (ie, not anticipated) and not an obvious variation of them.

Look at the claims of the patents you are concerned about (the numbered sentences at the very end). Is your invention different from the claims in any way? For example, suppose an existing patent claim discloses elements A, B, C, D, E, F and G. Your invention is A, B, C, D, E, F, and Z. Your invention is different and hopefully not an obvious variation of that patent.