Atm, Poser's IK is an all or nothing proposition, and unfortunately is kind of on the primitive side as well. That's one of the things that hopefully will get addressed in the future, as it seems more and more animators are coming out of the woodwork finally. And Rooster Teeth's use of Poser to animate RWBY.

Breaking an animation into discreet scenes is ultimately the most flexible way, as Richard said. Look at just about any movie, TV show, anime, etc, and time scenes with a stopwatch. 30 seconds is a long scene is CG or real life. You have to do a little planning beforehand, of course. The whole idea is to work out the flow on paper, decide what scenes you need, and only animate them, saving you a lot of time doing things you have to toss out in final editing for one reason or another. Once you have the scene list (just a table of seqential scenes and what is happening in them), if you have a clear vision of everything you want you can start keyframing. But professional practice is to do storyboards from that. Poser can and is used for that purpose. It lets you create a rough image or animatic of your story.....and if you build your sets for the purpose, just save the pz3's and you have your set ready for final animation and render.

The importance of a lot of these steps grow the longer your animation is, or how complex it is. You can easily get by with few or none of those steps if the animation is simple and short. The more complex, the longer it gets, the easier it is in the long run to devote a couple weeks to preplanning than waste 3 months keyframing and rendering scenes you never use.