Re: How should the water be in the vase?
You will have to experiment, to determine the water level. One inch above the stem output is a good starting point. Too much water, will make the draw difficult, too little water, and you do not get enough filtration nor cooling. I bought two ice trays at a specialty shop, that instead of ice cubes, it freezes the water into 3/4 inch spheres (balls). The balls are just the right diameter to drop into the neck of the water vase. The smoke pulling through the water, makes the ice-balls "dance" and the sound produced is a pleasant "clatter", that I find very relaxing.
You can also freeze your EMPTY water vase, prior to filling it with COLD water. I have heard of individuals using a small bucket, and placing the hookah in the bucket, and then filling the bucket with ice. Good Idea.