Panels have to face the sun to draw power. You get the energy from the sun, so it's important for the panels to be located in an area where they can get all the solar energy possible.
The best solar panels are able to be re-positioned to accommodate the seasonal shifting of the sun. But if you have to have a fixed panel, choose the best compromise between positions that you can.
A video presentation on Solar Energy, strictly on Photovoltaics (PV). These presentation is specifically based on a college project for an Engineering course.