Question
I buried a large container with 12000 gallons of capacity as a cistern. It collects
water from the roof. I am asking for advise on what kind of pump / controls /
valves and size of pipe can I install to automatically water the landscaping in our
yard.

Answer
Honestly, much of the information you request depends on the type of system you want, the size of area you need to irrigate, many factors.  I would consider a jet or centrifugal pump.  Any irrigation controller will work, but you will need a 24V to 120V relay to operate the pump with the controller.  You will need to install a foot valve on the bottom end of the suction line in the cistern.  I would use at least 1" pipe for the well and for the mainlines of the irrigation system.  1" or 3/4" valves are most common, depending on the number of heads and types of nozzles you select.  Remember to keep the demand GPM (what the sprinklers use) below the output GPM of the pump.  Say your pump supplies 18 GPM, make sure the sprinklers are putting out less than 18, but not too much less.  Information on all this and design guidelines are available from most irrigation suppliers.