SEAT POSITION

Height is one issue, position is the other.  When we talk about positioning, it's a built up process, first we start with the snare, bass drum and hi hat. Then add any other drums or cymbals we want to use.
   The Bass Drum. - It's best not to sit too close.  A good rule of thumb is to position your seat back far enough so that your knee is bent at about 90 to 100 degrees (between right angles or a little over over that to the floor) , so that your shin is about vertical or slightly sloping forward. This allows your ankle greater freedom of movement and thus gives you greater control over it.   Once we're found a comfortable distance.  We need to make sure we're sitting at a comfortable angle to our base drum also.   Personally a good rule of thumb, is to position your bass drum at about 15 degrees off center to you, so if you are looking directly ahead once seated, your leg would be at 15 degrees to your line of sight. (The 1 o'clock position)

  The Hi Hat - The same basic rules apply to the hi hat, don't sit too close, and try to position it slightly off center to your line of sight, about 15 degrees...  (The 11'oclock position)
   
  The Snare Drum - The snare should fit directly into front of you.  It's normally about 5/6 inches away from your crouch to the snare rim.  It's height should be above your knees, personally I like it to be about 1 or 2 inches about my knees. This lessens interference between your legs and hands while playing the snare drum.  Also, rather than having the snare perfectly flat, it's best to tilt it towards you slightly about 5-10 degrees, which makes it more accessible. 
   
  So once you've got your snare, bass drum, hit hat and stool positioned,  It's time to adjust the height of your high hat.  Personally, I like it about 5/6 inches higher than my snare drum, this allows me easily access to the edge and the top of the hi hat with both hands.