This article is from the Radio Control (R/C) Flying FAQ, by Shamim Mohamed firstname.lastname@example.org with numerous contributions by others.
Don't bother with the cheap 2 or 3 channel sets---get a 4-ch system.
It will come with NiCad rechargeable batteries and (usually) 3 servos;
this is the most popular and most cost-effective kind of system. You can
put the main pitch control (elevator) and the main turning control (in
this case the rudder) on one stick, which is how most people (and thus
most instructors) fly. The cheaper systems come with the controls on
separate sticks and you will have tough time finding someone willing to
teach you with that setup. They also use non-rechargeable cells, which can
get very expensive, and sometimes have corrosion problems at the terminals.