While working in the Pose to Pose Method
In step mode key every control on full poses- By keying every control for a pose you will be locking all of the elements of the character into position and keeping your curves clean. You will most likely not be utilizing every control, but you want to make sure that you are holding it's value. If you don't key it in and that control is used in a pose further down the timeline, eventually that value will drift over a series of frames causing floaty movement. Sometimes I do not include the facial controls when keying the full character.
Work clean- Keep track of what controls you are using to form a pose and try to stick to the same ones for your next one. By keying the same controls you will avoid animation curves that counter each-other.
Use tight break downs- Well what do tight breakdowns have to do with using curves? If you use breakdowns to fill in the gaps of your animation you will be relying less on the computer in-betweens. That way you will be saving your use of curves for what they are best at...refining.
When my keyframes are all set and I start breaking down my shot. I like to insert full breakdown poses on every controller on at most every 4 frames. When I set the break downs I am focusing on my transitions. Will this breakdown pose favor the previous pose and act as an ease out or will it favor the following pose and act as a fast out? Should I add a breakdown after my key that overshoots the pose? I keep these things in mind so that I use the posing of the character to dictate how the animation curves will be shaped.
Switching over- Once you have full poses on every control of the character on every 3-4 frames than you are safe to switch into a spline curve type. I like to use a spline type that will show a nice preview of my animation without having to clean up any tangent handles. I do this by using plateau tangents or spline with the auto-tangent script.
Hold off on offsetting- Once I switch over I will hold off on offsetting keyframes until I have taken a pass to tighten up the timing and posing. This is the first time I am seeing the animation on ones so there may be some tightening up to do. I will push full poses around on the timeline to adjust the timing and adjust the placement of certain body parts so that I can work some built in overlap into the poses. By working this way I am able to get my animation pretty far along before digging into individual curves.
Tie down your curves. -Usually, the first time i adjust animation curves on a pose to pose shot is the tie down. In this pass I will go through and edit the curves on the main body parts. (Usually the root spine and head, sometimes limbs) When I go through to clean up the curves I am looking for places where the curve is obviously not flowing like it is supposed to. For example maybe there is a curve that makes a hard transition that ends at two equal keys that form a flat. If I am not looking for a hard stop in my animation I will adjust that first keyframe that makes up the flat to ease out of the transition.
Cancel out counter animation- The tie down pass enables you to clean up your curves but it also serves as a pass to help you get familiar with what is going on under the hood and which controls are doing the heavy lifting. You should keep an eye out for counter animation during this pass. Counter animation happens during a transition where the value of one control cancels out the value of another. This tends to happen frequently on the rotate Y axis for Stewie and Bishop. If you see places where one control counters another see if you can remove the animation from one of the controls and add it to the other or redistribute the movement equally between the two controls.