Educate yourself. Start the education process by learning about the four Cs. “Understand how diamonds are evaluated and categorized,” says Brian Gavin, an internationally known diamond expert and co-founder of Whiteflash.com. The four Cs refer to clarity, cut, color and carat, and by understanding each, Gavin says, you can determine which is most important to you and then start shopping. “This will also help you determine how much you're willing to spend,” he adds.

Because education is important when engagement ring shopping, Whiteflash.com offers an interactive DVD, which features an in-depth look at each of the four Cs.

Get input. Find out what she wants. Gavin says, “It's better to be safe than sorry.” Take her to a jewelry store – that is, if marriage has been a topic of conversation and a surprise engagement is not on your agenda. “Have her try on as many rings as possible,” suggests Gavin. “Make her look at every shape of diamond and type of setting.” Another way to gauge whether she prefers pear-shaped over princess cut is have her look at bridal magazines like “The Knot” or “Brides” or at an online diamond expert's site like Whiteflash.com. “Either way, you'll know exactly what will make her swoon when you pop the question,” says Gavin.

If you're being discreet, look at the jewelry she wears on a day-to-day basis; is it classic or vintage in style? Is she prone to wear larger pieces or dainty? The other option is to ask someone close to her, like a sister or a best friend, for insight.

Let's talk carats. According to Gavin, as soon as you've decided shape, you need to look at the carat or weight of the diamond; carat is how diamonds and other precious gemstones are measured…in “carat” weight. One carat, for example, equals 1/5 of a gram. “We also refer to carat in points,” says Gavin. “There are 100 points in a carat and as points or carats increase, so does the price of the diamond.” For example, the price per carat will be less for a .90 diamond than the price per carat for a 1.00 diamond even if the color and clarity are the same. “Determining the size of the diamond, and then the cut and color is really going to help establish your budget parameters,” he says.

Pick a color. “Color is the third most important decision in the diamond selection process,” says Bob Hoskins, senior gemologist for Whiteflash.com. Diamond color is graded according to the Gemological Institute of America or GIA Color Grading Scale – D being the whitest, and N and below color ratings showing noticeable yellow tones. “E and F have no detectable color tones to the naked eye,” says Hoskins, who graded diamonds for the Gemology Institute of America (GIA) and taught several courses on colored stones. “And from G to J range, diamonds remain near colorless,” says Hoskins, “however, from J to M, you do begin to see a faint trace of yellow.”

A Cut Above diamonds or ACA, an exclusive brand of Hearts & Arrows diamonds available only through Whiteflash.com, range in color from D to I. Because of their superior cut, ACA even ‘face-up' appear whiter than their lab-assigned grade. “A great cut improves the apparent color of any diamond,” says Hoskins.

The cut and sparkle. Cut is the most important and perhaps the most misunderstood and controversial of the four Cs. “It's about more than the shape of a diamond,” explains Gavin. “When we talk cut, we're talking about the exact angles, proportions, symmetry and polish that affect the way the diamond reflects light and sparkles.” Diamond dealers also refer to cut as “make” – as it is the only feature of a diamond that can be controlled by man, and it must be precise. Each facet – or small plane surface on the diamond – must be cut to align perfectly with the facet opposite it. “There's not much room for error,” says Gavin, “because this affects the diamond's ability to sparkle, or what we call in the industry…brilliance.”

How important is clarity? Gemologists use a grading scale set forth by the Gemological Institute of America (GIA) to determine a diamond's clarity – how clean the gem appears when viewed through a magnifier. Most diamonds contain some “inclusions” – crystalline fractures or irregular crystal growth. The Gemological Institute of America GIA Clarity Grading Scale ranges from Internally Flawless (IF) through included (I3). Flawless (F) and Internally Flawless (IF) being the highest, with the next best grade being VVS1 and 2 or very slight inclusions followed by VS1 and 2, referring to very slight inclusions, which according to Hoskins, “are difficult to see even with magnification.”

SI1 and 2 diamonds will have slight inclusions, which are easily seen through magnification, but may remain clean to the naked eye, depending on the specific diamond. Hoskins says grades I1, I2 and I3 indicate inclusions that are visible under magnification and also to the naked eye. “The clarity of the stone you purchase will depend on your level of comfort and budget,” he says. His advice: Inclusions are more difficult to see in ideal cut and super ideal cut diamonds, because of the exactness in the cut.

Establish a budget. After determining the four Cs, you should be able to set a budget or at least have a figure in mind. The general rule of thumb is to set aside two months worth of salary. “If you're hesitant to set a dollar amount, look at your options in diamonds and settings to get a general idea of what you'd like to spend,” advises Gavin.

Select a jeweler. You have more options than the local jeweler around the corner. There are independently owned boutiques, national chains and now with the Internet revolution … online diamond boutiques like Whiteflash.com. No matter whom you buy from, make sure the jeweler is reputable and affiliated with the American Gem Society (AGS). “If you're unsure of the jeweler's credibility, check with the local Better Business Bureau,” suggests Gavin. “You can also test how knowledgeable the staff is about diamonds, look into customer reviews and look over the company's return and repair policies … this is important.”

Time to shop! Before you place the order, make sure that you will receive a grading report with your purchase. “If a grading report will not accompany your diamond, make sure the sale is contingent upon an independent appraiser's opinion,” advises Gavin. Another option is to ask for a fingerprint of the diamond. This is a three-dimensional drawing of the diamond indicating the four Cs, along with the stone's overall dimensions and enhancements. Inclusions and blemishes should be noted. “As soon as you receive the diamond, double-check all of the information, including the bill of sale and drawing to make sure that it is, in fact, the diamond you purchased,” finishes Gavin.

When purchasing from an ACA diamond from Whiteflash.com, customers receive the gem's certification and a signed letter of verification from an independent graduate gemologist appraiser for insurance purposes.

Set the diamond. If you purchased a loose diamond, you're now faced with the setting. And, like diamonds, the options are endless. Consider three stone settings, a solitaire or a custom design. Both Gavin and Hoskins suggest allowing four to six weeks before popping the question if you go the handcrafted route. If you're simply lost in the decision making process -- propose with diamond in-hand and pick out the setting later -- together!