We would start the effort of figuring this out by checking the basics, and then once we narrow down what system we need to concentrate on we keep drilling down to the answer.
To get an engine to run you need spark, fuel, compression, and oxygen. So we check for spark, and ultimately have to prove when that spark is occurring. Fuel, which means fuel pressure, injector pulse and fuel quality. Compression which also includes ensuring that the engines exhaust system is clear so that it can pump fresh air into the cylinders, (thats the oxygen part)
In order to pinpoint the cause of a given no start which could see the engine missing fuel, spark, or maybe both of them some quick checks are to see if the check engine light comes on when you turn on the key, and watch the security indicator to see if it is on or flashing. At the same time a scan tool is connected to pull trouble codes from all of the modules and that also allows the technician to monitor live data from the PCM. Ultimately this means you need a technician to test and prove what is going on, and if you like you can post the results of the testing back here for any additional input.