There are a number of reasons why a car may not start. The reasons for a no-start are related to fuel, spark or compression, as these are the required elements for engine ignition.
There are a few symptoms that give a clue as to why a car won't start. If the car is silent when the key is turned, it could be the battery cables, or on a vehicle with a manual transmission, it may mean the clutch isn't depressed. A clicking sound when the key is turned almost always means a dead battery. If the car cranks, but won't turn over, then the fuel supply may be suspect. Check fuel injectors, the fuel pump and spark plugs to make sure they aren't fouled.
If the engine turns over then immediately dies, it may be related to a choke being stuck on a carbureted vehicle. On a noncarbureted vehicle, the problem likely requires professional help. Another possibility with cars that won't start on rainy days is that the distributor cap may be damp. Cold-start problems may be related to the battery or carburetor on vehicles that have them. Other starting related problems include missing while idling or hesitating on acceleration. These problems may be related to plugs, plug wires, fuel pump, fuel injectors or the distributor.