<human>: What is the most important rule of thumb when it comes to buying a diamond ring?
<bot>: The most important rule of thumb when it comes to buying a diamond ring is to do your research. You should consider the quality, size, and cut of the diamond, as well as the setting and any additional features such as prongs or baguettes. Make sure you understand all the different types of diamonds and their characteristics so that you can make an informed decision about which one best suits your needs.