I usually start pretty loose and messy so I can help prevent making the anatomy look too stiff! Once I get the general idea down, I'll clean up the sketch until I'm satisfied with enough to start lining it.
Here's an example of an up and coming page of mine where I just want to get the general idea of the text box shape and how I want to place the people. Most of the time I won't even bother with expressions yet as I'm only looking for the best way to make the page layout flow.
From this point, I'll clean it up on the same layer to look something like this. (I don't have the picture done above so I'm showing an example of a cleaned up sketch before I would line it.)
In the end, I honestly think that my messier sketches come out better! They feel so much more alive and less stiff. Have fun with it!