You're not a jeweler. Why would you have ever needed to know about loose diamonds?

It's important when choosing anything to be as educated about it as possible, just to ensure that you are getting the best value possible. Nothing pleases a salesman more than to come up against a customer who is uneducated about his product. No intelligent haggling will be had.

So, learn the value yourself. Here is a short tutorial to help you along. 

Your first question might be, "Why would I even find myself in possession or search of a loose diamond?"
That is a valid question. One main answer is that having a loose diamond allows you to create custom pieces of jewelry. You are the master of your own creation instead of having to search for that "perfect something." 

Additionally, bands and fittings can hinder the ability to appraise a diamond well. You may be under the impression that you are purchasing a certain caliber of diamond when, in reality, you were blinded by the band (and so was the appraiser). Self-design allows you to have your diamonds properly appraised before setting them into the band that will signify your life together. Alternatively, you could just get some really great earrings or a necklace out of the deal. Each to his or her own. 

When on the hunt for diamonds, keep in mind the 4Cs: Cut, Color, Clarity, and Carat weight. 

Cut: When they come straight from the earth, raw diamonds are not at all glittery. Professional diamond cutters take care of turning them from drab to fab. Generally, they fall under three different categories. Aim for the third. The first type of diamond is known as a shallow cut. Their size allows for darkness to pool at the bottom, reducing shine. Deep diamonds let light slip out the sides, which causes them to dull in appearance. Finally, there are the ideal diamonds. These diamonds allow for outer cuts and inner facets to catch the light no matter where you turn. 

Color: You do not get to have any influence over the color of your diamonds, as that is determined by the variables in the earth where they were created. What you do have control over is which diamond you select. Whites are winners. The whiter the diamond, the more valuable it becomes. 

Clarity: Clarify refers to whether or not a diamond has become scratched or damaged on its journey from creation below the earth to mined and on the counter in front of you for inspection. Look for diamonds you can see through easily, without any debris or major scratches. 

Finally, check the Carat weight. This is the measurement of the weight of the size, the weight of a diamond. Do not allow yourself to be deceived into believing that just because a diamond is large that it is also super expensive. You could be looking into purchasing a large diamond at a lower price and think you are getting a steal. Check the clarity and cut, though. There could be a high number of defects that are lowering the cost. 

Loose diamonds, in every shape, size, and color, can be made available in every price range. Just know beforehand what you are getting into, and you find yourself with a great product at the price you deserve to pay.