One other point; before installing the servo arms on the servo, make sure the servo is at neutral (stick and trims centered). This is accomplished by powering the transmitter and receiver with the servos connected to the receiver. Afterward, place the servo arms 90 degrees from the servo, unless differential is needed. This method results in equal servo movement in each direction. Bear in mind, this setup is for control surfaces only, the servo arm for the throttle servo is typically setup with the throttle stick at one end (or the other), that is throttle fully opened or throttle fully closed.

DaveB