Mistake: Sticking to conventions.
Yes, conventions are good to stick by much of the time, but occasionally a shake-up is in order. Here, the oblong dining table sat square in the middle of this room, leaving space for little else. But flipping it sideways and scooting it to the end of the room left space to incorporate a buffet and secretary (not shown).
Mistake: Forgetting creature comforts.
Think about what you’ll be doing as you use the furniture. Having coffee tables and side tables within reach of all seats for drinks puts convenience at the forefront.