Furniture on wheels is easy to move out of they way or use in another room.
Keep your furniture away from the walls even in small spaces.
Find creative ways to divide spaces.
Don't skimp on light fixtures. They finish a room, draw your eye up and make a room feel larger.
Buy the right sized furniture for the space. Not too big not to small, just right.
Keep accessories neat and organized and if you rent remember that when you design with accessories you can take them with you when you go.