1997 Nissan Altima won't start

If your getting enough fuel and adequate spark then the next step is to check for compression and timing. Assuming you don't have a security system installed or a factory one.

Checking for compression requires a special tool to measure how much pressure each cylinder is creating

Timing you would need to remove the timing cover and make sure all the timing marks are lined up in the correct positions. If not then the belt has jumped teeth possibly causing internal engine damage.