For individual servings:
Boil your water for tea, and put the tea bag of choice (I've even done herbal tea) into your mug. Fill the cup only about half-way, and let steep for about 10 minutes (to get a really strong brew).
For a whole pitcher:
Put about 7-10 bags of tea (preferably black or decaf) into a small saucepan (7 bags for 3 quarts, 10 bags for 1 gallon). Pour boiling water over them until they are just covered. Let tea bags sit for 15-20 minutes, to allow them to steep and make a very strong, condensed brew.