How to Choose a Diamond
To choose a diamond, get the highest quality cut you can afford since this will impact the gem's brilliance. An "ideal cut" is the best quality, but a "good cut" is cheaper if you're on a budget. Additionally, ask a jeweler for the diamond's clarity grade, which refers to how flawless the stone may or may not be. If you're looking for a flawless gem, you'll want a grade of FL or IF, but know that these gems will also be the most expensive due to their rarity.
Pick out the right shape for you and your budget. While cut refers more to quality and level of brilliance, the shape is one aspect of the cut. Review the possible shapes available on the market, and choose the one you like best. If buying a diamond for someone else, ask his/her opinion before selecting a shape, or bring a trusted friend/family member. Select a popular, classic shape if you have no one to ask. The most popular shapes are round brilliant, princess, and cushion cut. Consider a non-traditional shape if the receiver has a non-traditional personality. Also, note that less common shapes can be 30%, for the same karat weight and quality! Less common shapes that are still fairly popular include marquise, oval, pear, and heart. Choose the highest quality of cut you can afford. A diamond's cut determines the vast majority of its brilliance, and many consider the cut to be the most important factor when choosing a diamond. Ask the jeweler to see the Gemological Institute of America's (GIA's) diamond grading report for any diamond you consider purchasing. This report will give you a rough grade on cut: Select an "Ideal Cut" diamond for the highest level of perfection. Choose a "Very Good" or "Excellent" grade diamond for a slightly less expensive yet high-quality stone. Consider a "Good" grade if you want to balance the other C's and still stick to a budget. Never purchase a fair to poor quality diamond, especially for engagement rings and other gifts. Diamonds at these levels severely lack brilliance. Consider the number of chevrons. The pavilion side is the lower side of a diamond, which isn't visible enough and has no impact on its sparkling style. Chevrons are of particular importance when considering the princess cut diamonds. These are the facets at the pavilion side of the diamond surrounding the main pavilion. Most princess cuts have two, three or four chevrons. The more the chevrons, the more the light gets reflected upon. There is no "right" number of chevrons, just personal preference. More chevrons lead to a more multifaceted look, whereas less has a smoother look. Ask the jeweler about the clarity of any diamond you consider purchasing. Diamonds are dressed in a considerable amount of sparkle and brilliance, making a diamond's inclusions less noticeable. The various clarity levels associated with diamonds are F to IF, VVS1 to VVS2, VS1 to VS2, SI1 to SI2, I1 to I3. A reputable jeweler will be honest about a stone's grade and will answer any questions about what that grade means. Buy flawless, FL, or internally flawless, IF, for stones without any internal imperfections. These are very rare, though, and very expensive. Consider VVS1 or VVS2 clarity grades for high-quality diamonds with very, very small inclusions that are invisible to the untrained eye, even with a 10-power magnifier. Look at VS1 or VS2 grades for diamonds that are flawless to the naked eye with very minor inclusions. Consider a diamond with an SI1 or SI2 rating for a stone with small inclusions that are still invisible to the naked eye, but easy to spot with a magnifier. These stones appear high quality to the vast majority of individuals looking at them, and are also less strenuous on your budget. Purchase a diamond that balances colorlessness with the price. Since most tints are extremely difficult to see, a higher grade for color does not make much difference in quality. It can, however, make a huge difference in price. Select a D grade (blue white) for an absolutely colorless diamond only if the price is of no concern. Look E or F diamonds ("ice white" or "fine white," respectively) if you cannot afford a D grade diamond but still want a stone that is colorless with any band, on any skin tone. Diamonds rated H, I, and G are considered white, with H representing the top quality white. Note that, while these diamonds appear completely colorless, they do have a light yellow tint against a bright white background. That said, this tint disappears when set into a metal band, as no metal is solid white. Though still white or colorless against most backgrounds, J - M diamonds run from "top silver" (J) to "light cape" (M), a cheaper silver coloring. When set on a colored band like gold, they appear colorless, though they may have a tint on whiter metals like platinum. Ask the jeweler about a diamond's fluorescence. Fluorescence appears when a diamond is exposed to ultraviolet light, but usually has no effect on a diamond in regular light conditions. On rare occasions, strong fluorescence can alter the appearance of a diamond's color, sometimes causing it to look milky or oily. Consider a diamond with medium fluorescence or strong fluorescence if on a tight budget, since these diamonds are often discounted. Consider a "fancy" diamond, a type of rare stone with an especially deep hue. This is for the high-rollers out there, as these diamonds are expensive. They will, however, stand out from the crowd. Red and pink fancy diamonds are rare, beautiful, and expensive -- and the most popular "fancy" diamond. Take karat weight into consideration last. This does not affect the quality of the stone in any way, so a heavier weight does not necessarily indicate a higher quality stone. Note, however, that this may not be possible on a budget. Do you want a slightly smaller stone at higher quality, or the opposite? Consider selecting an uncommon size karat to save money without sacrificing quality. The most common sizes for engagement rings are 1/2 karat, 1 karat, and 2 karat. People often choose common karat weights, which are known in the industry as 'magic weights'. Because they are common, the price of diamonds at these weights is usually disproportionately higher than diamonds just below the magic weight e.g. a 0.98 karat diamond may be significantly less expensive than a 1 karat diamond, with no visible difference in size. If buying an engagement ring or gift, find out what the recipient prefers in size. Not all women prefer many karats. Some may place quality over size while others may be willing to sacrifice a bit of quality for a more noticeable diamond. Ask the recipient herself about her preference. Ask close friends or family about the recipient's preference. Consider the size of the wearer's hand if buying a diamond ring. Women with more petite hands may prefer the look of a smaller stone to larger stones that have a tendency to overwhelm. However, women with larger hands may drown out a small stone, making it appear smaller than it really is. Choose a band metal. Make a list of the precious and long-lasting metals. Here, it is important that the band material lasts just as long as the stone. Metals like gold, silver and platinum are not only beautiful but last long for years. Choosing among them is usually a balance of beauty and budget. Gold is perhaps the most common band, as it looks great with any stone or skin tone. Look for gold and its variants like yellow, rose and white gold to further customize the ring to your hand. Silver is yet another metal that is affordable and suits almost every skin tone. Out of the various variants of silver, sterling silver is the best comprising of 92.5 percent pure silver, and 7.5 percent mixed alloys. As such, it is the most affordable and a durable ring band option. You can go for platinum bands if budget is not a problem for them. Platinum is considered as the most lustrous of all precious metals and is getting widespread popularity for diamond and engagement rings. Know that higher karat rates have stronger, more scratch resistant bands. Considering karat weight when making gold band selection is important. 24 karat gold has the highest amount of pure gold. Moreover, due to the higher amount of pure gold, 24 and 22 karat gold are softer than 18 or 14 karat gold. creating a greater chance for jewelry to scratch or bend. Pick a setting. Assuming you're choosing a diamond for a ring, you will have a choice about what kind of setting to place it in. The cut you picked will be a big factor here. For example, on a princess cut diamond, you'll want to choose a setting that protects the stone's corners. Add accent stones if desired. You'll want to make sure you match the color and grade of any accent diamonds to the center stone since that is your focal point. These are usually smaller diamonds or even other colored jewels. Set a budget before you start shopping. Doing so will help you choose the highest quality diamond you can find for your money. Diamonds are expensive, and salespeople might try to upsell you if you're not prepared. Make a budget and stick with it. Do a little online research before heading to the mall to judge prices. It is not terrible to shop over two days. Use the first to see prices across different jewelers, then come back the next day to make your purchase. Do your research. Learn as much as you can about diamond quality and price to prevent yourself from getting cheated. This can also help you bargain a little bit, especially if you know the grades, ratings, and color information in the steps above. Shop around to compare prices, and check online for deals. Visit several different jewelers for a wider selection and price range. Always ensure that you compare prices, and that a price that you are offered is fair. It's a good idea to compare any price that you are quoted in a brick and mortar jeweler to the price of an identical diamond from a reputable online retailer, as can be up to 50% savings to be found on an identical diamond by buying online. Ask to see official grading reports, such as a GIA report, before purchasing a diamond. While your personal preference is important, don't let yourself get scammed into paying more than you want. Once you know you like the diamond, check out the grades on the GIA report before plunking down a ton of money. 
Pick out the right shape for you and your budget. Choose the highest quality of cut you can afford. Consider the number of chevrons. Ask the jeweler about the clarity of any diamond you consider purchasing. Purchase a diamond that balances colorlessness with the price. Ask the jeweler about a diamond's fluorescence. Consider a "fancy" diamond, a type of rare stone with an especially deep hue. Take karat weight into consideration last. Consider selecting an uncommon size karat to save money without sacrificing quality. If buying an engagement ring or gift, find out what the recipient prefers in size. Consider the size of the wearer's hand if buying a diamond ring. Choose a band metal. Know that higher karat rates have stronger, more scratch resistant bands. Pick a setting. Add accent stones if desired. Set a budget before you start shopping. Do your research. Shop around to compare prices, and check online for deals. Ask to see official grading reports, such as a GIA report, before purchasing a diamond. 