The difference between a great cup of tea and a bad cup of tea is in the details.  Throwing a tea bag into a cup and adding boiling water is easy but at best you get a mediocre cup of tea.  With only a little more time and attention you can have a great cup every time.

1. Know your tea.  The variety of tea is what determines how much you use, how long you brew it and what temperature water you use.
2. Use the correct amount of tea.  The general rule of thumb is to use about a teaspoon of loose leaf tea for every cup of water.  However lighter teas such as green or white can take up to twice as much.
3. Heat your water to the correct temperature.  Black, dark oolongs and herbal teas do best with boiling water.  Green, white and light oolongs do better with very hot but not boiling water — about 160-190 degrees.
4. How long you steep or brew your tea is a bit like what Goldilocks experienced.  If you steep your tea for too long it will become bitter.  If you don't steep it enough then it will be weak and underflavored.  The 'just right' amount of steeping creates a tea that is full of flavor without any bitter notes.  The general rule for black teas is about 3-5 minutes.  White and dark oolongs can be steeped up to eight minutes while most greens should not be steeped more than three minutes.

The table below provides a quick reference:

One last thing to know — how big your tea cup is.  A traditional tea cup usually holds about 6 ounces of liquid.  A large mug can hold up to 12 ounces of water.  I often brew my tea in a pyrex measuring cup so I can measure the exact amount of water I want.

Keep in mind that as tea brews it 'grows'.  A teaspoon of dried tea leaves often expands to 2-3 teaspoons after brewing.  The popular tea balls are convenient but they don't allow enough space for the water to circulate properly around the tea leaves.  For the best results brew your tea with either a large strainer basket that can be removed or allow the leaves to remain loose and strain into a cup for drinking.

During the winter months when you want to drink tea throughout the day brew your tea in a pot using a strainer basket.  A tea cosy will keep the pot hot for longer.  For a single cup you can brew your tea in a measuring cup and then strain into your cup.