First (ideally) you would have the model done, and already textured. So you could see where and if the textures and mesh stretch badly when you animate.
Second, you need to create a series of bones (or "joints" as they're often called ... all of which can be named anything you like, for easy referencing, like "Left_Forearm" and "Right_Foot") These bones will usually stim from the "Hip" joint. The first joint you put down is also called the root joint, because moving it will move your entire model. Once you've got all your joints created, and joined together properly, you can go to actual rigging.
Third, you need to make those joints/bones influences you model. Most programs can do this in one of two ways. Either Smooth or Rigid. Smooth "binding" will assign vertices to multiple bones, giving the illusion of organic motion and a smoother bending. Rigid "binding" will assign each vertice to only one bone (usually the nearest by default) and when you rotate these joints, a very harsh line can somtimes appear. "Binding" is the process that will take your skeleton (all the bones) and assign the vertices to the bones, making the vertices move with the rotation of assigned bones. By default sometimes programs will assign the nearest vertices to every bone, but usually this isn't good enough, so you have to go in, select each bone and re-assign the vertices properly to get the best results.
Usually I use a combination where most vertices are assigned only to one bone, except the vertices near joints. Like an elbow joint with all rigid binding would cause a horrible hard-line at the elbow when you bent it. So the joints around the elbow are assigned only 25-50 percent influence at the actual joint, the rest of that influence goes to another bone (in the elbow's case, I would assign the rest of the influce to the Shoulder bone just above it.)
When you're done rigging, you can start with the animation (fun fun!) In almost every program out there, "keyframes" are used save animation data. If I want a walk animation, I start at the first frame, rotate all my joints to a proper mid-walking position, and before I do anything else, I hit "Set Keyframe" or the equivalent in your program. Next, I copy that keyframe to the end of my animation (say it's frame 20, for the sake of abstraction) at frame 20, and paste that Keyframe. Now my guy only has two Keyframes, but the animation lasts 20 frames. I go to the middle of my animation, frame 10, and rotate the bones to the opposite stride of my walk, and "Set Keyframes" again. This is a crude walk, but it's for demo only
Now, if you hit the play button, you will see your models leg do a back/forth psuedo-walk. All that's left to do is go in and tweak the unnatural look of the walk to make it better, but you can add as many keyframes as you want (one keyframe per frame per joint) to get the animation done. The program should fill in the blanks in between the keyframes so you don't have to actually set a keyframe for every single frame.
Hope this helps, and doesn't confuse!
-Tyler
P.S. This is what the alphabet would look like if Q and R were eliminated.
