Brewing tea can be simple or very complicated.
I believe tea should be brewed to personal taste. Some love bags and some love loose tea or both.
Three main considerations are the type of tea, water temperature, and steeping time.
If you have loose tea start by measuring. 1 - 2 teaspoons per 8 ounces cup of water.
However, if the herb is fluffy such as chamomile or white tea you may have to use 1 tablespoon. Dense teas may take less than 1 teaspoon. Let your personal taste decide though. Place the tea bag or tea in an infuser with measured tea directly into your cup/ teacup. Some people choose to place tea directly into the cup they are using.
Heat your water to temperature. Use filtered water whenever possible and not water that has been set in a kettle or your tea may taste flat. Catch your water at just boiled and pour over tea.
Steep your tea using this guide as a general rule. Brewing too long can extract bitterness from your tea leaves. You can reuse teabags.
Herbal tea 3-5 minutes
Green tea 1-3 minutes
Black tea 3-5 minutes
White tea 3-5 minutes
Rooibus 3-5 minutes
Mate 3-5 minutes
I generally cover herbal teas so the essential oils stay in your cup. For all other teas, covering helps keep in the heat.