Consider the equipment
Ask for brochures of the products. Many manufacturers produce competitive, comparable components. However, some also make inexpensive items too. If it looks flimsy and cheap, it probably is.
Make sure your contractor is installing a backflow preventer and that it is the proper one for your yards installation. Different elevations in land mean that different backflows may be needed. Be sure that permits are issued if they are mandatory in your town. Ask if a licensed plumber will be doing the work.
Be sure the contractor gives you a written estimate. The bid should describe the product to be used, the quantity of each, at least on major parts such as sprinklers, valves and controllers. Insist on a rain sensor to stop watering in rainy conditions.
If designed and installed correctly and with quality products, a sprinkler system will give you many years of service and value with minimal maintenance.