Electrical problem
1996 Range Rover V8 All Wheel Drive Automatic 135000 miles

I have a 1996 range rover 4.6 hse, an it will not start! I was driving to the store an I came to an idle an my rover sputtered then died an never started back up, it will crank but will not turn over, what are some things that I could troubleshoot an fix on my own or should I go take it an get it diagnostic tested? I have done all minor procedure such as changing the battery went got my alternator tested an it was good dont know what steps to take now, please help!