For you it might mean a full cradle to cradle zero of minimal waste cycle, design for a long life, repairability, maintenance, considerate material choices including Organic, recycled, OEKO Tex, the absence of fluorocarbons in waterproof garments.
For us we tend to ask questions, especially when it comes to gifts such as is it needed, will it be used, is it wanted, is it longlasting, is it repairable, can it be recycled at the end of it's life, is it worth passing on when you've finished with it, will it end up in landfill.
Extended warranties that are well backed up such as the Victorinox lifetime guarantee or the Leatherman 25 year warranty are a good sign that the product is designed to last.
Some items may be choices that make a bit more sense to us such as a battery powered light stick, I have used the same one for night kayaking for 12 months now, when the batteries go I can recycle them and replace the battery, rather than throwing away a light stick every time I go for a paddle.
Some brands really work hard on their environmental impact and we have highlighted them in the Greener Brands Section and include all their products in the Greener Gear Section.