WORKING FROM A GIVEN KEY POSE
In any "professional" animation production, the animator does not just make up the first pose in any scene they are given to animate. They are given a scene folder which will (should) contain the following items:
• Storyboard panels for the scene
Ideally, there should be a start pose for the character that indicates where the character is placed within the environment, their size relationship, their attitude and eye direction. Depending on how much action is going on, there should be a pose for every major point in the scene, not key poses, but indications of where the character is moving from and to. If the character enters the scene by walking through a door, there should be a pose of the character as they are in the middle of opening the door. If the character then walks across to a table and picks something up, there should be a pose of this action as well. If the character exits off the edge of the field, there should be a pose showing the character at the exit point.
If there is a scene that comes just before yours, and there is a "Match Cut", where the final pose must match to the first pose in your scene, you really need to have this final pose from the animator in order to begin your scene. If the two poses don't match you'll end up with what is called a "Jump Cut" which is not a good thing.
Let's say the final pose in the previous scene has the character ending with their finger pointing up into the air to accentuate the dialogue. If you begin your scene with the character scratching their nose, the actions will not match up and the character will appear to jump into the different pose suddenly... hence the term, Jump Cut.