Lay out on a scaled drawing of your property all physical features such as house, patios, pool, slopes, path of sun, soil types, and chemistry. Next plan the landscape considering both the mature size of plants and their spread as well as fill-ins prior to maturity. Your plant selection as well as soil conditions will determine what changes you need to make to the existing environment.
You can convert your plan to a water requirement map. Delineate trees that may require deep but infrequent watering. Outline zones needing frequent shallow watering like grasses. Identify plants that require daily misting (if any).
Once you've identified all demand zones you can start laying out specifics of your irrigation scheme. The heart of a good plan is a good controller. For only a few hundred dollars you can purchase a controller that can control up to 24 automatic valves and run up to 24 different programs using any of those valves. For example, a valve that irrigates hanging begonias may be programmed for two minutes three times a day, while your fruit orchard can be irrigated for three hours every 14 days. Typically you can apply a percentage increase or decrease to an entire program to account for seasonality. You can even obtain sensors which tell the controller that it is raining. Essentially, the options available will exceed any need.
The placement of automatic valves around the yard requires some thought as well. Usually it is easier to place the valve near the area to be watered, eliminating all the extra piping. You do, however, have to run the signal wire (low voltage) to each valve.
The number and type of sprinklers and drip heads is enormous. Drip heads flow at rates from one-half a gallon per hour up to 30 gallons per hour. Drip tapes and soaker hoses have similar rates. Sprinklers range from mini sizes which require less than a few gallons per hour up to impulse heads consuming many gallons per minute. Don't expect to run several impulse heads off a single one-half or three- quarter-inch line.
The secret of beautiful landscapes is also the secret to water conservation: make an irrigation plan that puts water where you need it - not anywhere else.