Sprinkler systems make the task of keeping the lawn green ten times easier. When watering is automated the lawn receives consistent water and at the best time of day, which early in the morning. Watering early in the morning (4-6 a.m.) keeps evaporation from the sun to a minimum, but does not allow the water to sit for long enough to promote mold.
Each spray head should have a filter in the body to catch pieces of debris. Bits of sand and dirt can clog the spray head and result in odd or weak spray patterns. Pull the filter out of the riser and clean it up or replace it. Look for brown spots in the lawn to locate suspect spray heads.
To clean a clogged spray head get a piece of fine stiff wire. Use the wire to dislodge the particulate stuck in the spray port. It is best to perform the operation while the water is running so that the debris is flushed out of the system. Consider repositioning the canister a little bit higher if a specific spray head continually has problems.
If all the sprinklers are weaker than normal it is probably a leak. If possible, make a map of the underground plumbing in the sprinkler system. Use the map to do a walk around to check for wet spots. Wet spots usually indicate a leaky pipe.
Most sprinkler systems come with some sort of timer control. It sends an electronic signal to the valves to open and close each zone. The sprinkler system is typically split up into multiple zones so the proper pressure can be applied to each zone. If all zones turned on at once the low pressure from the city main would most likely not be able to properly operate your home's system.
There's not much maintenance to be done here. Make sure the back-up battery is replaced once a year. It is best not to wait until it dies unexpectedly. The other task to do is turn the system on in the spring and off during the fall (in addition to other winterizing steps).