My CRJ-200 lessons learned:

-- Do not sit in a window seat, ever. Doubly true if you are stocky or broad shouldered. The wall will shove you against your neighbor.

-- 1B/C is the best possible seat on the plane.

-- Getting moved back because of weight issues is ok if your flight is not full, as many times there will be an open row or two back there. If they ask for volunteers to get moved, unless you are in a big hairy rush to exit the plane when you land (well, most of us are given how crummy this plane is, but moreso than usual), take note of how full it is in back and volunteer if you get an open row.

-- Do not sit by the lav.

-- Do not even try to use the lav.