Keep the blade vertical. If one side of the blade cools faster than the other then the blade will warp. I use a quart of 30 weight motor oil poured into an old bread pan. Motor oil is cheap but it stinks. David Boye's book says he used olive oil at one time.
Water quenches the blade more quickly than oil and gives a greater risk of warpage or cracking.
If you didn't get the steel hot enough before quenching it will not be hardened. Try to scratch the blade with a file. If you can scratch it then the blade didn't get hot enough. Sometimes the thermal stress created by quenching is so severe that the blade will spontaneously crack. Consequently the next step, tempering, should be done very soon after the blade has been quenched and hardened.