Find out what angle to set your solar collectors at.
When you can't afford a full system, instead start with a solar water heating system. Water heaters make up a large portion of the energy that a home consumes during the year. Your costs are going to be lower upon installation of your solar water heating system.
Carefully consider the types of solar panels you plan on having installed. Long ago, if you didn't have enough roof space, you'd need very expensive high efficiency mono-crystalline panels. There are now more advanced polycrystalline panels and even thin film panels. If you've got enough roof space, you might wish to look at the size of the panels in relation to their output capacity to avoid having insufficient panels that you need more of later.