Proposing is tough enough, but finding the perfect ring, set with the perfect diamond is even tougher. It's important to know what you're buying. Here are some tips to help you make the right choice.

* Educate yourself. Start by learning about the four Cs: clarity, cut, color and carat. 'Understanding how diamonds are evaluated and categorized will allow you to determine which is most important to you,' says Brian Gavin, co-founder of Whiteflash.com, an online diamond and jewelry boutique specializing in Hearts & Arrows diamonds.

* Get input from your fianc'. Visit jewelry stores together and try on as many rings as possible, and note which cuts and types of settings she prefers, or look at rings in bridal magazine or an online diamond boutique. If you're being discreet, look at the jewelry she wears on a day-to-day basis or ask someone close to her for insight.

* Let's talk carats. Precious gemstones are measured in carats. '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.'

* Pick a color. D denotes the whitest, and anything N and below show noticeable yellow tones. 'E and F have no detectable color tones,' says Bob Hoskins, senior gemologist for Whiteflash.com. 'From G to J remain near colorless, yet from J to M, show faint traces of yellow.' A Cut Above diamonds or ACA, an exclusive brand of Hearts & Arrows diamonds available at Whiteflash.com, range in color from D to I.

* The cut and sparkle. Cut is the most important and perhaps the most misunderstood and controversial of the four Cs. '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, explains Gavin.'

* How important is clarity? Clarity refers to how clean the gem appears when viewed through a magnifier. Most diamonds contain some 'inclusions'crystalline fractures or irregular crystal growth. 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 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 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). Test the staff's knowledge, look into customer reviews and at the company's return and repair policies.

Before you place the order, make sure that you will receive a grading report. '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: Ask for a fingerprint of the diamond. This is a three-dimensional drawing of indicating the four Cs, along with the diamond's dimensions and enhancements. Inclusions and blemishes should also be noted.