A mini-tip to expand on Joe's suggestion: When working with a range of keyframes in the graph pallette, try moving the range of keyframes with the CTRL key pressed while IK is on, such as moving the ytran for the hip while IK is on for the legs. You can use it to make a figure crouch more or stand up straighter throughout an animation. Also works for arms, such as keeping hands in place over a keyboard then adjusting the bend keyframes for the chest or abdomen to make the figure hunch over the keyboard more (or less).