I love this post by Michael at Inspired by Charm as he gives some wonderful decorating tips that can be applied to many pieces in your home. The principals he follows were adapated by Justina Blakeny...
Function – what you need this space to do.
Color – stick within your color palette.
Shapes – use a variety of shapes to create balance and add diversity.
Texture / Pattern – use different ones to create visual interest.
Spacing – the different between collected and cluttered, leave some empty space.
Foliage – flowers and plants complete a space.
Sparkle – add something that sparkles – glass, metallic, mirrors, crystals, etc.