Normal cranking, but no start can be caused by various systems:
ignition system, fuel system, etc. If you are having slow cranking, the
problem is with the battery or starter.

To check ignition system: Open hood and look for disconnected
spark-plug wires or vacuum lines. Crank the engine and check if each
disconnected plug wire is producing spark when close to engine body. To
start with the fuel system: press the valve on top of engine to see if
fuel is comming out.

For futher info:
http://www.hintsandthings.co.uk/garage/diagnosis.htm