1. Hanging artwork too high. I see it all the time and I’m afraid I will go to my friends’ homes and point this out (they thank me for it, most of the time). There must be something in human nature that says hang it up high, but think about it: art is there to look at, so it should be at eye level. Stick to this rule and you’ll find it all works much better. Go and have a look at where your art is. Is it too high? Does it make sense?
2. Buying rugs too small and placing furniture around them, not on them. My rule is this: buy rugs as big as you can afford. Put your furniture ON them, not around them. There are always exceptions to every rule but, in general, this approach looks and feels much better, grounds your furniture and defines spaces within multi-use open plan areas like living/dining rooms.
3. Forgetting about lighting. Lighting is key. It’s so important when it comes to creating a layered interior. It’s another layer all on its own. Overhead lighting, in most living areas, sucks. It might work in kitchens and bathrooms but it is often too harsh in living areas and does little to create ambience. Consider table and floor lamps at different heights and brightnesses to mix it up. Install dimmer switches where you can.