The best peice of advice I can give you is to learn from real life.

Watch how people move. Watch weight, ease, timing. Count how long an action takes from start to finish. Count the amount of actions it takes to complete a move. Break things down into their contituent parts and start one move at a time. Some actions start slow and pick up speed, some start fast and ease to an end. But they will all have a begining a middle and an end so those will typically be your primary keyframes.

As for technical info on animating in Poser, the manual pretty much has everything you need as does the SmithMicro site - They have a few tuts online as well. Poser is not all that complex a tool for learning animating, albeit somewhat convoluted.