Checking Brake Fluid Level

WARNING: This page is about a different car, the 2005 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

Check fluid level in reservoir tank. It should be between Max and Min lines on reservoir tank.
Visually check around the reservoir tank for leaks.
If fluid level is extremely low, check brake system for leaks.
Release parking brake lever and see if brake warning lamp goes off. If not, check brake system for leaks.

Fig 1: Checking Brake Fluid Level
Courtesy of NISSAN MOTOR CO., U.S.A.