turn the key to the on switch DONT TRY TO START IT UP. just try to keep it on the on switch until 30 sec. look at the odometer to see if you get any code like NO BUS codes or something. oh one thing does your gauges work?
By start do you mean it doesn't crank over at all which is most likely a starter/starter solenoid problem. If the vehicle "cranks over" but doesn't "catch" the problem could be many things ranging from fuel to spark, some basic diagnostic tests would need to be done. Even if the check engine light is not on, attaching a scan tool may derive valuable information.