Checking Brake Fluid Level

WARNING: This page is about a different car, the 2007 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

Check fluid level in the sub tank. It should be between "MAX" and "MIN" lines on the sub tank.
Visually check around the reservoir tank and sub 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: Locating Brake Fluid Level
Courtesy of NISSAN MOTOR CO., U.S.A.