How do you adjust the driver side window on a 1993 Nissan 300zx to prevent air and water leaking inside?

Over time the rubber along the edge of the window will shrink. Open the door and rub some Vaseline on the rubber. Leave the door cracked and leave the Vaseline on there over night. In the morning wipe the Vaseline off with a clean dry rag. The Vaseline expands the rubber causing a perfect seal again.

If the car has been wrecked in that area then you will need to take the door apart and adjust the window stops which are located across the top of the door. There are two of these.