The first thing you need to do is look at the type of business you are dealing with, for example, hotel, air line, public utility, etc. You can then create a web search in Google, Bing, etc. like, “What type of business is Con Ed” and you will receive a reply like regulated utility. You can then crate a search like, “Who are the regulators for Con Ed”. You will then see the various state agencies you might complain to, based on the specific issues you have. If the issue is service it would be one agency if the issue is billing it could be another. Once you locate the agency you want to complain to you can go directly to their web site and often file your complaint there or you may find an email address where you can send your complaint. If the issue is with a bill or a fine you may want to scan in the document in question to support your claim. You will of course want to cc the company or organization against whom you are complaining. This will often get much more attention from the company then just a complaint to the company. If you do file a complaint directly with the company it will be useful to cc the appropriate regulatory agency.