I just started an animation degree program at my community college, and learned that all forms of animation(3d, drawn, claymation...) follow the same principles.
You need...
anticipation - move the arm back before you swing
ease in/out - your swing will first speed up...be sure not to move anything at a steady pace. It never looks right
overshoot/settle - ex. when a character stops walking, his momentum keeps moving foreward and then setles back.
followthrough - ex. the head will still be moving a few frames after the body has stopped.

there are a bunch of great books on drawn animation out there and the same principles can be used in 3d. I suggest you take a look at any of the following

Disney Animation : The Illusion of Life - Frank Thomas and Ollie Johnston
Animators Survival Kit - Richard Williams
Timing for Animation - Harold Whitaker and John Halas


In all of these books it says that there is no rule for "how many frames" something takes or how big the motion should be. There is no formula. It all depends on the motion you are going for. Is it a friendly slug on the shoulder? An old man with a lazy swing? The knockout uppercut in the boxing match?

Like the other guys said, try the action you want yourself. An animator is an actor. Also do it a bunch of times with a stopwatch to see how long it took you. The best part about Maya is of your a little off, its very easy to tweak the motion.