principle #1 
Salvage, reuse, reclaim or repurpose it. Attempt to give everything—a chair, a half-used can of paint, reclaimed wood flooring—a second life, especially if it’s made from natural materials. When you reuse items, there’s less demand for new goods—which means less mining, logging, milling or manufacturing in the long run. You can find many materials—from floor tile to bathroom fixtures—at construction exchanges or local salvage yards. 

principle #2 
Choose natural and renewable. The best natural choices for your home are made from rapidly renewable resources including wool, wheat, bamboo or cork. Wood is renewable, but it takes decades to replace a tree. Stone is not renewable, but it requires less embodied energy (the amount of mining, smelting, machine-working, firing, processing or shipping required to make something) than metal. Most natural materials will eventually biodegrade or disintegrate when disposed of. 

principle #3 
Buy recycled. Recycling diverts trash from landfills and gives it new life. Glass and metal may be melted down and refabricated. Wood recycling, however, could more accurately be called "downcycling," meaning the resulting product is of lower quality than the product that went in. Recycled wood becomes wood pulp, which becomes paper, which becomes recycled paper.

principle #4 
Seek out the least harmful option. Some products don’t fall into any of the sustainable categories but still might be worthwhile choices because they cause less harm to the environment than their conventional counterparts. Examples include paints that have lower emissions of toxic chemicals (called volatile organic compounds, or VOCs) or carpet squares that can be returned to the manufacturer for recycling.