The bottom line - do your research, understand exactly what you're looking for, and then go to Diamond Source to get the best stone at the best price. The guys are open, honest, have gorgeous stones and a return policy. What are you doing? Go to Diamond Source!
Now more for those of you worried about spending thousands of dollars on a rock...
First, a couple of pointers about buying diamonds in general. Do. Your. Research. Learn everything you can about diamonds. The 4 Cs? You're kidding, right? Understand the components of the 4 Cs. Want an example? Let's take color, that's simple. So a diamond is an F. What does that mean? D, E and F are white diamonds. Unless they are next to each other the F will look white just as the D does. That means an F is the best value of a diamond that, to the naked eye, will look white. Cut. The cut is 'excellent.' Great. Did you know about symmetry and polish? What about lower pavilions? All of these components factor into how brilliant a diamond shines, which at the end of the day is probably most important. There will be controls. For example, to my fiance the size of the diamond was important. I'm not Bill Gates so I didn't go buy a huge D color, Flawless clarity, ideal cut triple X stone. I educated myself on what I could look for in a stone that would do the most to get that "shiny sparkle" my fiance wants without blowing my budget (and Diamond Source sold me a gorgeous stone - more on that later).
Once you understand what's important in finding a brilliant diamond look at Blue Nile. A LOT. Visit a lot of jewelry stores. Ask great questions based on what you now know about diamonds. Buying diamonds, like participating in any market, is about information. Diamond dealers have more information than you. This favors them. By educating yourself you level the playing field and you'll see better diamonds at a better price. If you walk into a store and immediately share your budget, you'll see a lower quality diamond at that price because they need to make money. This is why it's important to go a lot of jewelry stores. Go in ones you don't think will have the best diamonds. That way if you say something stupid, or share your budget too early, you aren't ruining your chance at the place you're actually going to buy the stone at.
Now you're ready. Now you go to Diamond Source. Igor and Vlad are great and have beautiful stones. Read that again - they HAVE stones. What do I mean? If you walk into a diamond dealer's store and ask for a stone and he says "ok, let me call my guy I'll have it in 15 minutes" or asks you to make an appointment then he is getting diamonds from a broker. This isn't the end of the world, but it will cost you more because the broker isn't a retiree doing volunteer work - this is his job. If you can look at dealers' diamonds (that they own) you can get a better price because there's no broker. Diamond Source has a gorgeous selection of their own stones. I'm also confident they could get diamonds from brokers and still give you an incredibly fair price.
Diamond Source is also very honest and open. You need to know which questions to ask and they will give you straight answers. They want you to find a beautiful stone (and guess what? they have them!). Unlike most dealers on 47th, there is no pressure to buy. What else is great? 30-day return policy. Seems obvious, right? Actually most dealers only except exchanges. Most probably wouldn't sell you a fake diamond, but what if they did? You're screwed. Not at Diamond Source. See, this stuff is important.
Other important points - my fiance had very specific requests about the ring, the sizing, the look. I kept her involved throughout the process and we were able to come look at the actual rings (I purchased the wedding band at the same time as the engagement ring) before the diamonds were set to make sure they were exactly what she wanted. The guys were awesome. What more do you need to know? read more