Karl-Friedrich Hohl \ Istock

1. Do you really need it?

Facing economic stress unprecedented in our lifetimes, we might not need this reminder the way we did a couple years ago, but it's always a question worth asking. Separating your "wants" from your "needs" is a good first step toward reducing the environmental impact of your purchases (not to mention the financial impact on your wallet). The environmental impact from buying comes primarily in the use of natural resources to manufacture the products in the first place. If you don't buy it, you eliminate its impact.

In the case of jewelry, the mining of precious metals and gems has one of the biggest environmental and human impacts. Gold mines represent the largest U.S. sources of mercury pollution, a potent toxic metal that attacks the brain. Diamond mining is notoriously tied with slave labor and the funding of systemic violence in Africa. Beyond that, mining anything involves not only tearing up a landscape, but also processing that typically uses toxic chemicals and metals. Avoiding unnecessary purchases avoids those impacts.

Clothing, meanwhile, relies largely on cotton crops, which account for 10% of the world's pesticide usage. In the United States cotton is commonly grown with more than 10 pounds of pesticide per acre annually (that's more than three-times as much chemical as is used to grow conventional corn). Conventionally grown cotton also uses a whopping 142 pounds per acre of chemical fertilizer (much of it derived from natural gas, a fossil fuel).

2. Can you get it used?

Many products have a useful life that extends far beyond the needs of one owner. Many products can ably serve more than one master at a time. Ask your friends and neighbors if they can share. Before buying new, check local garage sales, thrift and antique stores, classifieds, auctions, clothing swaps -- and their global online equivalents, freecycling, Craigslist and, of course, eBay -- to look for items that can be given a second (or third, or fourth) life. Bottom line: Buying used is the most environmentally sound way to buy, because it not only requires the use of no new natural resources in manufacturing, but also because it keeps a useful product out of a landfill or trash incinerator.

3. How was it made?

Particularly if you're buying new, consider how a product was made: what materials were used, who made it and how were those workers treated? It's often not the end-user or the end-user's community that suffers from the manufacture of products that aren't made according to high environmental standards, but workers and local communities and ecosystems near the factories. eBay has made this step easier by bringing together ethical buyers and sellers via World of Good, which uses independent certifiers to ensure that only products that adhere to high environmental and human rights standards are offered for sale.

In the case of clothing, look for sustainable fibers like wool, bamboo and hemp, USDA organic-certified cottons fibers, and fabrics made from recycled materials, such as fleece made from recycled plastics. How clothing is made, and who makes it, is another concern. Green America has a useful list of companies that allow unions so you can avoid clothing made in sweatshops. Also check out the lists of companies that meet the standards of the Fair Labor Association and Social Accountability International.

For jewelry, 80% of newly mined gold ends up in retail jewelry, so the No Dirty Gold lists retailers that support better human rights and environmental protections at the world's gold mines. Diamonds, as Leonardo DiCaprio brilliantly reminded us in Blood Diamond, have often reached the consumer market only after a violent march across Africa, and the money spent on diamonds has ultimately fueled wider bloodshed. Unfortunately, the problem didn't end with the movie, so Amnesty International and Global Witness have published four questions consumers can ask jewelers to get some assurance that the diamonds being bought are "conflict-free":

  1. How can I be sure that none of your jewelry contains conflict diamonds?
  2. Do you know where the diamonds you sell come from?
  3. Can I see a copy of your company's policy on conflict diamonds?
  4. Can you show me a written guarantee from your diamond suppliers stating that your diamonds are conflict-free?

World of Good and etsy.com can be excellent sources for independent and ethical clothing and jewelry.

4. How is it packaged and shipped?

The making of a product is only part of what contributes to its environmental footprint. The materials used to package it, and the fuel used to transport it, are two other biggies. Studies have generally endorsed the proposition that online purchasing has a smaller environmental footprint than buying from a brick-and-mortar store, in large part because of the reduced energy costs associated with lighting and heating. Look for goods packaged minimally, and packaged with post-consumer recycled materials. If packing something of your own for sale on eBay or elsewhere, get creative: Crumple the paper that you'd otherwise have recycled to protect fragile items. Set aside a few boxes as you come across them, so you can reuse them when you need them. A minimum of thought can save significant resources over the long term. If you are buying from a brick-and-mortar store, ask questions of the store manage, or consult the company's Website for information about how they manage the efficiency and wastefulness of their supply chain.

5. How much energy or resources will it require to maintain?

The environmental impact of newly purchased items doesn't necessarily end when you get them home. Clothing needs to be washed, and jewelry shined. Buying a new dress that you can run through the washer has less impact than one that must be dry-cleaned, for instance, since many dry cleaners clean with toxic solvents.

6. Can it be reused, mended or recycled?

What happens to that product once you're done with it? Is it durable enough to be of use to your grandchildren? Can it have a second (or third or fourth) life once you're done with it? If it breaks, do you have the means to repair it?

Not only does it save resources to buy durable clothing and jewelry, but it can also provide a good return on investment. When you've tired of that necklace or dress, you can sell it to recoup some of your costs -- or even turn a profit. But often that's only possible if you've purchased a good quality item with lasting value.

7. Does it help me go green in other ways?

The crown jewel of ethical buying comes if the purchase you make helps you maintain a green lifestyle. That may mean supporting local artisans with a purchase of a painting or piece of jewelry. It may mean buying a piece of clothing that lets you wear your passions on your sleeve -- and educate friends and passers-by in the process. Or it may be as simple as buying a good raincoat ... so you can walk instead of taking the cab on rainy days.

Finally, maybe the purchase itself contributes to a cause, because the seller donates a portion of proceeds. Check with the organizations you support to see which companies they work with, and get in the habit of reading the environmental and sustainability sections of companies' Web sites. One great way to connect with sellers that share your passions -- and who will back up that passion with a donation based on your purchase -- is via eBay Giving Works.