Determine your budget.
This is a very personal exercise that obviously depends a lot on income. The most important rule of thumb is to choose the finest-quality diamond you can afford. The price of a diamond depends on its particular combination of the four Cs. With a wide range available, you're sure to find one that suits your personal taste and budget. Just remember one thing: unlike a car or other household purchase that will depreciate or that you expect to replace some day, a diamond truly is forever. It will be a treasured symbol of love and commitment for decades to come.

Educate yourself.
Although the average couple spends somewhere around $2,000 on a diamond engagement ring, not many of them know about the four Cs: Cut, Color, Clarity and Carat weight. Make sure you understand these four characteristics that determine a diamond's quality and value, and, as a result, its price. No two diamonds are alike, although they may look identical to the naked eye.

Do some style research.
With so many options available, from classic solitaires to imaginative, one-of-a-kind designs, couples should shop together for their rings. Shop around. Look at (and try on: you won't know what really suits you until you see and feel it on your hand) different gems and styles in different jewelry stores before selecting your rings.

Grooms-to-be should consider this: surprise her with a romantic, unusual or unexpected marriage proposal, but do not surprise her with a ring! If she absolutely hates the one you've chosen, you'll both end up feeling hurt and resentful - not exactly the way you want to begin your engagement. Remember: she'll be wearing that ring for the rest of her life, so she should really love it. (Obviously, the same rules hold true for a groom's ring.) If you're determined to surprise your girlfriend with a diamond engagement ring (and 55 percent do), do some research on her personal style and preferences. Take her fantasy shopping. Talk to her friends. Watch what makes her gasp in awe. Ask how she feels about other rings she's seen.

When selecting an engagement ring, remember that it will be paired with a wedding band later on. You may want to choose your rings at the same time to ensure they complement -- and fit comfortably with -- each other. Ask your jeweler about engagement-wedding ring sets, rings that intertwine or fit together like pieces of a puzzle.

Find a reputable jeweler.
The fifth C is Confidence in the professional who will help you choose a diamond of enduring quality to represent your enduring love. Choose a reputable jewelry store where you feel comfortable and that offers you a fair price - preferably one holding a diploma or certificate from an organization such as the American Gem Society, the Canadian Jewelers Institute, the Canadian Gemmological Association, or the Gemmological Association of Great Britain. Ask the jeweler questions until you've established a good rapport and feel you can trust him or her. Remember: if a deal seems too good to be true, it probably isn't such a deal.

Protect your investment.
Make sure that your purchases are properly and fully described on your bill of sale; if you are buying a particularly valuable piece - a diamond ring, for instance - you should have it appraised to verify the facts on the bill of sale. This appraisal will provide important information to the police and your insurance company if the piece is ever stolen and, depending on the terms of your insurance policy, will ensure that a lost, stolen, or damaged item is replaced with one of comparable quality. Consider having your valuable jewelry re-appraised every few years to keep up with increases in gem and precious metal prices. Once you've had your jewelry appraised, shop around insurance companies to find the one offering coverage that best suits your needs.