My business partner and I just researched and made the same decision. The factors we felt were most important included: filing fees, taxes, business friendly laws and statutes, and our physical location. Delaware, Nevada, and Wyoming are often listed as the top states to incorporate. Delaware is often selected because it has some of the most pro business statutes. Nevada has low taxes and filing costs.
Physical location can be very important. If you incorporate in Delaware and are physically located in another state - you will be classified as an out of state filer in Delaware, may pay additional filing fees, need to appoint a registered agent in Delaware, qualify as a foreign filer in your home state, etc. As a result, Delaware's benefits may be more applicable to a large, public corporation.
In addition, we found that taxes will be determined based on your business transactions, assets, and other factors. As such, incorporating in a state with low taxes does not necessary mean you will pay low taxes. You will also need to register in each state you conduct business (e.g., material sales, recurring sales, assets, employees).
There are lots of factors to consider. A good CPA can prove to be a valuable resource in making this decision.