I have a few additions to the information in this article. The main thing I want to mention is security systems. I've had plenty of issues with aftermarket security systems causing no-starts. If you have an aftermarket security system and a no-start condition you’re trying to determine the cause of, be sure to include a look at the security system.
Also, some factory security systems can cause a no-start because they don’t recognize your key. The way many of these systems operate is by talking to your key when you try to start the vehicle. If the security system doesn't recognize your key, it will disable some vital part of the engine management system and your engine won't start. Obviously, this is to prevent theft, but there are times when these systems fail and cause a no-start condition. Usually when this happens you see a flashing light on the dash indicating that the security system has disabled the vehicle.
Honestly, the best way to handle this is to take it to a dealer. These systems are proprietary and are set up to only work with factory equipment. Some independent shops are equipped to handle situations like this, but not many. Be sure to call ahead and ask if the shop you're taking your no-start to is capable of communicating with the immobilizer system on your vehicle. If not, they won't be able to service the system and you'll have to take it to someone who can. There might be a workaround somewhere for your vehicle, but you'll have to do your own research to find that out.