Facing true south in an unobstructed location is extremely important to the proper functioning of a solar electric system
If your site is in the northern hemisphere you need to aim your solar modules to true south (the reverse is true for locations in the southern hemisphere) to maximize your daily energy output. For many locations there is quite a difference between magnetic south and true south, so please consult a magnetic declination map before you setup your mount structure. The solar modules should be tilted up from horizontal to get a better angle at the sun and help keep the modules clean by shedding rain or snow. For best year round power output with the least amount of maintenance, you should set the solar array facing true south at a tilt angle equal to your latitude with respect to the horizontal position. If you plan to adjust your solar array tilt angle seasonally, a good rule of thumb is:
Most mount structures are available with a seasonal adjustment of the tilt angle from horizontal to 65°. To determine if your proposed array site will be shaded at any time of the day or year you should consider using the Solar Pathfinder.