Freezing temperature can be harsh on the lawn sprinkler system and lead to costly damages, so it is imperative that you winterize these systems before the temperature dips. Doing this, you can avoid breaking of components that occurs due to freezing and expansion inside the valves, sprinklers and pipes. Here are some tips to help you winterize your lawn sprinkler systems.

• Deactivate the timer: If you have an automated sprinkler system, make sure you deactivate or reconfigure the settings. This will stop the system from turning on. You can either set the controller into ‘rain mode’ or completely shut it down. However, when you cut the power supply, the preset data is deleted and you need to reprogram it when required.
• Drain the water: All the lawn sprinkler systems have a drainage system, so make sure you drain the water out of the sprinkler system to avoid it freezing during cold months. 
• Shut off the water supply: It is crucial to shut off the main valve of the sprinkler system and insulate it. The valve should be made freeze proof by placing it below the frost line, and wrapping it with insulation. Also, insulate any exposed pipes and backflow valves. 
• Blow out the system: To winterize the system, mechanically introduce air into it and remove all the water. If you are unable to manage this task on your own, consider hiring a professional sprinkler repair company. If you do plan to do it this on own, then you must have the required equipment and you should also know how to do it safely. Make sure you use the right type of air compressor.
• Remove backflow preventer: It is essential to remove the backflow preventer from the system to avoid backflow. You can either siphon it or pump it out with the help of a vacuum. Narrow the opening by attaching duct tape and draining above the ground valve. You can also use pipe-heating cables to prevent backflow.
• Remove the hose from the hose bib: If the hose that connects to the hose bib has water, it can break when the temperature drops, so make sure to remove the hose from the hose bib and close the valves to prevent any leakages.

You may also refer to YouTube for videos you can view to be shown how some of these processes can be done step by step.