Diamond jewelry is a significant purchase, but it's not one that needs to be scary.  Armed with some basic information, you can buy diamonds with confidence, either for yourself or a very special someone else. 

1. Do your homework.  Familiarize yourself with some basic terminology like the Four Cs (cut, color, clarity and carat weight).  Know which options are most important to you.  Here's a quick overview:
   
   
   • CUT determines the stone's fire and brilliance and is probably your most important C.  Not to be confused with a diamond's shape, cut refers to how a diamond's facets are created to maximize the amount of light that is absorbed, redirected, and released.  Nature controls the other 3 Cs, but a diamond's cut is in the hands of the craftsman who shapes it.
       
   • COLOR is also an important consideration.  Diamonds can be colorless (the most desirable, and therefore the most expensive) to brown, with a whole range of whites and yellows in between.  It's important, when buying a piece with multiple stones, that the colors are all a good match.  Colors are designated with a letter, with D being colorless and Z being light brown.  Avoid stones that appear "milky."
       
   • CLARITY designates how flawed or included the diamond is.  While flawless diamonds do exist, they are rare and very expensive.  Avoid any stones that have black flecks that are visible to the naked eye or that have chips, cracks or feathering when viewed under a gem scope.  A diamond's clarity is described as F (flawless) VVS (very, very slightly included) VS (very slightly included) SI (slightly included) or I (included).
       
   • CARAT Weight is based on a scale of 100 with 100 points equaling a carat.  A 25 point stone is a quarter carat, a 50-pointer is a half-carat, etc.  Size should really be the last C you worry about-it is far better to have a smaller, less-flawed, beautifully cut, near-colorless stone than it is to have a 3 carat that has no fire or sparkle. 
   
   
2. Know how much you want to spend before you leave home.  It's easy to get caught up in the glamour and prestige of diamond jewelry.  If you set your budget firmly, you'll be better able to stick to it and avoid overspending.
        
3. Choose your jewelry store wisely.  Rely on recommendations from friends and family or a local jeweler's reputation.  The jewelry industry is plagued by retailers who falsely inflate their prices to create phony "sales," and trick you into thinking you are getting a great deal.  You are much better off patronizing a jeweler who rarely or never runs sales, and whose prices remain steady throughout the year.  If a sales associate starts talking about the store's financing options or how easy it is to open a charge account before you even see any diamonds, this is not the place for you to shop.
     
4. There is a proliferation of online diamond retailers.  While some of these websites might be a good place for you to start your research, it is really better to make your purchase from a brick and mortar shop.  Why?  If you break a prong, or lose a side stone from your mounting, it's a little difficult to return the piece to the internet for repair.  Likewise, the internet isn't likely to offer complementary inspections, cleaning and polishing.  In addition, no two diamonds are alike; each one has natural characteristics that make it unique and it's very hard to see subtle (and not so subtle) differences between stones when you look at them online.

Do your research, visit several jewelry stores and ask questions.  You'll be surprised at how quickly you become comfortable with the 4 Cs and making that diamond-buying decision.