We preheat ovens to make sure we bake at a consistent temperature and the same methodology applies to brewing the perfect cup of hot tea. As you probably already know, the three components of making tea are:
Amount of water
Temperature of water
Brew / steep time
Your cup can go awry if you don't dial in those three critical parts of the brew process. Right now, we're going to focus on #2, the temperature of the water. To figure out the best temperature for your tea, it is absolutely a trial-and-tweak process, but most teas you buy have basic instructions telling you where to begin.
For Embrew tea, we have the instructions on the front of the bag and for ours, since there is already a natural sweetener inside the tea bag, we recommend brewing 10-12oz of water rather than the typical 8oz of other tea bags. This is because we add extra ingredients for a larger cup (we're all drinking out of larger mugs these days) and to achieve just a hint of sweetness, a little more water is important.
If you use a temperature controlled kettle, like we do, it helps you be more consistent in Step 2 of brewing. Early on in my tea life, I checked the temperature of my tea brewing a few minutes after I started and was surprised to see that there was a significant temperature drop (like 10 degrees!) after only two minutes.
This is when I went looking to the tea pros and found the proper gong fu brewing technique where I learned that they pre-heat their gaiwan or tea pot before the brew with tea leaves. This ensures that heat is not lost when you start with a room-temperature cup.