Your patio can take a entirely different dimension after the sun sets, and adding lighting can enhance the experience. While custom-created and installed systems are available, it's just as easy, and less expensive, to create your own.
One of the best ways is to purchase old strings of white and colored Christmas lights, specifically the ones with the tiny bulbs. String these through trees, in plantings, even around the patio itself. The strings can be dressed up in a number of ways. Many people use small plastic bottles as covers for the lights. The lights are inserted through the bottle's mouth, and floral tape is used to hold the assembly together. The bottles can be cut in a design, and markers used to add color and visual texture.
Another way to light the night is with a fire bowl. Check if you need a permit to use one first. Also check the area above and around where the bowl will go -- you don't want errant sparks setting off a fire. A cheap fire bowl can be made by removing the legs from an old charcoal grill and setting this firmly on a set of stone or bricks. They can also be made from old steel restaurant mixing bowls or the drums from large truck brakes. Look around for anything that can take the heat from the fire without melting or igniting.