Make sure that all equipment is well maintained and in good repair before letting your child loose on the playground. Keep them away from broken equipment or playground items that look dangerous or meant for older children. Beware of twisted or rusted metal.
Also check for unsafe surfaces. Avoid playgrounds with concrete, asphalt, blacktop, or packed-earth surfaces. Instead, find surfaces loosely filled with materials like wood chips, mulch, sand, or shredded rubber.
Source: Flickr user avrene