Human: What is the most important rule of thumb when it comes to buying a diamond ring? Assistant: 
The most important rule of thumb when it comes to buying a diamond ring is that you should always buy from a reputable jeweler. Make sure they are certified by an independent third-party organization and have a good reputation in the industry. You should also take the time to research different types of diamonds, including color, cut, clarity, carat weight, and price range. Finally, make sure you know your budget before making any decisions so you can be sure to get the best deal possible.