A mountain bike is made of numerous parts and each of them can affect your riding experience and comfort. Therefore knowing how to adjust these components would ensure that your riding experience is safe and relatively comfortable.
The first thing is to make sure that your choice of the bike allows you to not just adjust the height of the saddle but also tinker with its position.The correct way to do it is to seat yourself on the bike and adjust the height so that your feet are able to touch the pedal when it is at the bottom possible end of the stroke.
The idea is to adjust the position and height such that A) your knees bend slightly as you pedaling motion and B) you are able to pedal without tilting to either side.
Seat Tube Height
The seat tube in an MTB houses the seat post that can be adjusted. Typically when you stand on the pedals, the seat bike seat should offer you the necessary space to orient your body accordingly.
So an inch of clearance from the horizontal inclining tube is what is needed at the minimum. Anything less and you could face a lot of unpleasantness while negotiating a bumpy trail.
While this might be a personal preference based on one’s riding style, it is nevertheless important to understand how the handlebar height affects your riding experience.
Basically, if your handlebar height is lower than your seat height, it will help you attain a streamlined position thereby helping with longer rides on smooth surfaces. Conversely, a higher handlebar height makes it easy to move the bars but it will also mean that you are taking away some of the weight of the front suspension.