Step 1: Decide How Much Tea You Want and Measure Out Your Ingredients
I usually do about 1/4 of the total, so if I want a gallon of tea I'll heat a quart of water. There's no need to measure or be exact; just put some water in a pot.
If you're just making a single serving of tea, put a half cup or so into a glass and pop it in the microwave.
The important thing is to use the full amount of tea. If you're making a gallon, use a gallon's worth of tea. For loose tea the usual recommendation is one teaspoon per cup. There are 16 cups in a gallon, so that's 16 teaspoons, or a little more than a quarter cup.
I put it all into a jelly bag, but you could use just about anything. You could even dump the tea straight into the water and strain it out after, the old fashioned way.
If you're using bags, use about one per cup of brewed tea that you want.
It's better to use too much tea than too little. If your beverage comes out too strong you can always add more water, and remember you'll be serving this over ice! It's a lot harder to strengthen tea that's too weak.
Step 2: Heat the Water and Make the Concentrated Infusion
Once the water boils, add your tea. Steep it for the same amount of time you would if you planned to drink the tea hot. I usually do about five minutes. A bit longer will make the tea stronger and extract more caffeine, but I wouldn't go longer than 10 minutes or your tea will be too bitter.
Step 3: Pour the Concentrate Into Your Pitcher
Step 4: Top It Up With Cold Water
Fill the container up to the level of the amount of tea you used the leaves for. In other words, if you used enough tea leaves or bags to make a half gallon of tea, fill the pitcher so you have a half gallon of liquid total. Don't add a half gallon to your pint of concentrate or your tea will be weak and watery.