reprinted courtesy of ServiceMagic.com

This information can clarify and help answer some questions.
Landscaping considerations: You'll want to let your service professional know if you're planning on installing the sprinkler system under existing landscape. It's more work and will cost more than if the landscaping is being done later.
Circuits: Sprinkler systems are planned so that areas that need the same amount and type of watering will be on the same circuits.
If your service professional knows which areas (grass, flower beds, trees) need the same kind of watering schedule, he or she can decide better how to arrange your system for maximum impact.
Timer: If you desire a time clock so you can time your watering periods, let the service professional know in advance. Likewise if you'll need trenches beneath driveways or pathways, let him know ahead of time so he can include that in his plans.
-- Tips courtesy of Service Magic