Wow, could be a hundred things. Might be a weak battery - have that tested at an auto parts store. Then you should check spark at the plug while cranking (pull the plug wire from the coil, stick a screwdriver into the end and hold close to a metal component). Don't touch the metal part of the screwdriver unless you're looking for a wake-up call. When cranking, a spark should arc between the screwdriver and the metal part. No spark - might need to replace the coil. If spark, I would look at fuel system delivery, i.e., check pressure at the fuel rail. If no pressure, I would then look to the fuel pump (under the rear seat - passenger side).