Locate the instructions that came with the lights. If you threw them away or can't find them, don't panic. Try to remember the way you assembled the lights when you installed them. You're about to take them apart the same way to access the solar panels. If you've worked with garden lighting before, then this will not present a problem for you. If you're a novice with regard to solar lighting, be careful with the disassembly.
Take the battery out of the light fixture and make sure there is no oxidation where the plastic and the cell pack come into contact. If you find oxidation, use a small soft brush to gently remove the residue. Oxidation looks like the substance you see when regular AA batteries explode. It has a whitish, ashy tint. If it has been more than a year since you replaced the original solar battery, do so at this time.
Clean the solar collector panel once a month and wipe the dirt from the top of the panel. Look for bugs and tiny garbage and remove these. Use a damp cloth and wipe gently.
Check the surrounding area for preventive maintenance. If your solar garden lights are under bushes or trees, trim the branches back. Clean the panels after heavy wind and rainstorms. In the winter months, ice is likely to form on the ground, and you don't want your solar lights out in this type of weather. Bring them inside until the weather warms up, and you'll extend the life of the lights.