Actually, Mike McKinley has an excellent tutorial on character rigging which will show you EVERYTHING! Kurt Boutilier also has some excellent tutorials on the subject of animating rigged characters.
The basics, however, are as follows.
Joints are either controlled through FK (forward kinematics; you pick the joint itself and rotate it to where you want it) ir IK (inverse kinematics; a series of joints, such as a leg/foot combo, are connected with an IK handle. Manipulating this handle moves the entire series of joints). One can switch from FK/IK freely.
If you wish to mirror a pose on an opposite limb (as for a walk cycle), you can either "eyeball" it, or for more accuracy do it in the channel box. Pose your left leg, for example, and then enter the same values in the channel box (NOTE! Enter a negative value for the opposite limb in "x" and/or "z"). This should "mirror" your pose. BTW this only works if your character is centered on the grid.
Most "basic Maya" books also cover this subject. It does take time to master animating in Maya, but the results are more than worth the time taken to practice!
"Ad astra per aspera..."