Question: I keep cranking but the engine just turns and does not want to start. What is happening ?

When cranking, if the engine spins freely and does not "catch", you can be pretty sure that it is flooded. A way to confirm this is to take out a spark plug: if it is soaked with gas, the engine is definitely flooded. Note that the more you crank, the more flooded it gets, so it is wise to stop cranking as soon as you realize that you are flooding the engine. This will make starting much easier.

Because unflooding an engine requires quite a bit of starter cranking as well as maximum rotating speed, the battery should be fully charged before you attempt the method outlined below:

remove the top (when looking from the driver side fender) two fuses in the fuse box next to the driver side shock tower (this will disable the fuel pump and the ignition)
crank the engine for 5 to 10 seconds (not more) with accelerator pedal fully depressed (to the floor) (this will eliminate the gas in the chambers)
put back the two fuses
crank the engine without depressing the accelerator pedal (get ready to depress the pedal when the engine catches and keep it there)
do this a few times until the engine starts (if not successful, keep reading)
remove the top two fuses
remove the spark plugs (you may want to dry them up if wet with gas)
crank the engine for 5 to 10 seconds with accelerator pedal fully depressed
add a spoonful of motor oil into the chambers through the leading (bottom) spark plug holes
crank the engine for 5 to 10 seconds with accelerator pedal fully depressed (this will coat the chambers with oil and restore compression)
put the spark plugs back
put back the two fuses
crank the engine without depressing the accelerator pedal (get ready to depress the pedal when the engine catches and keep it there)
do this a few times until the engine starts (if not successful, keep reading)
if you are still reading, then you should probably recharge your battery and try again (good luck though)

There are three main reasons why flooding occurs (in random order): leaking injectors, weak compression (older engine), and/or low cranking speed. Leaking injectors should be professionally cleaned. To prevent injector leakage, a remedy is to remove some pressure in the gas line when the engine is off. This is accomplished by installing a "fuel cut-off" switch in line with the the fuel pump relay. You then use the switch to turn off the engine (instead of the key) and relieve gas pressure in the line.

The diagram above shows the fuel pump relay (left) and the connector (right). The connector is a yellow plug located under the steering column towards the right. The switch is installed by cutting the B/W (black with white stripe) wire and connecting the two cut ends onto the switch.