Ok, you have spent a few days "flying" on a rc flight simulator and now you are ready to go live. One of the best ways to learn the ins and outs of flying rc model planes is to work with an experienced pilot as an instructor who can show you the ropes. Once you have chosen an instructor you have a couple of options on how you work with them.
One option is to use the old fashioned approach where the instructor starts off with the controls and can pass the transmitter over to you to allow you to take control of the aircraft. Typically the instructor will first go through take off, basic flight maneuvers, and landing as he explains to you what he is doing with the controls and how he expects the aircraft to react as he moves the controls for the throttle, rudder, ailerons, elevators, landing flaps, etc.
The next step would be for the instructor to get the aircraft airborne and into a stable flight pattern and then hand the transmitter to you as he provides verbal instructions to you to maneuver the aircraft. If you begin to get into trouble with the plane the instructor retakes control of the transmitter. Obviously this approach has a few drawbacks - having to pass the transmitter back and forth can be cumbersome and at times too slow.
A "buddy box" solves this problem and is one of the best tools available to the novice pilot to allow both an experienced pilot and you to have access to the controls on your model plane at the same time. Most buddy boxes are set up so that the instructor is in control of the transmitter and can quickly allow you to control the plane or can take back control if necessary. With a buddy box system you actually have two separate transmitters that can send signals to the aircraft. The two transmitters are typically joined together by a cable and the instructor has a spring loaded switch that he pushes that allows your transmitter to take control. As soon as the instructor releases the switch his transmitter is on control again.
More sophisticated buddy boxes allow the instructor to maintain control of some channels, each channel controlling a specific component on the model plane, like the throttle for example, and the student to control other channels. This is a particularly effective way of teaching a novice pilot to fly because you can begin by having control of the "easier" aspects of flying the plane while the instructor maintains control of the more sophisticated controls.
Within the RC flying community there is debate on whether using a buddy box is the best way for an instructor to teach a student pilot how to fly. Some pilots believe that learning to fly a RC model plane is best taught by having the student learn the "feel" of the stick so they can do the right stick movements to get out of a bad situation or make a good landing. So the argument is that the student doesn’t really get the feel of the right movement when it is critical because the senior pilot bails him out. But for my money, if my choices are it takes me a little longer to learn to fly, or I watch my $500 investment dive into the ground – well, you can make your own choice...