Low voltage irrigation systems utilize a 24VAC electronic signal to initialize a valve's solenoid. Even though the system is lo voltage it is still always recommended a trained professional perform these tests.
Checking Voltage at Controller
Using the AC voltage reading on your volt meter, touch one probe to the station terminal you wish to test and the other probe to the C or COMMON terminal while the station is activated. Typically it does not matter which of the two colored probes goes where, but for consistency purposes use the black probe for the C terminal and the red probe for the station terminal.
With the station activated and this icon showing; (icon).
Checking Voltage at the Solenoid
Use the same AC voltage reading on your volt meter as used on the controller. It is no coincidence that the solenoid has two wires and the controller had two screw terminals for you to test.
Solenoids have two wires, one for the COMMON wire and one for the station's power wire. Typically COMMON wires are shared throughout irrigation system's to save on wire.
Place the black probe from the volt meter on what's presumably the COMMON wire at the valve manifold, place the red probe on the solenoids power wire. With the station activated you sould have 24-28VAC.
Note: Be sure that you have good contact with the wires when leaving the wire nuts on as pictured here.