It's dead-simple: make tea and put the sugar in while it's hot, then cool and ice it. That's all. Maybe some mint, maybe a bit of lemon.
But some sort of magic happens, and you end up with a pitcher of this beverage about which poems are written, which brings to mind slow lazy sitting-on-the-porch days and gracefully sprawling oak trees, which prompted legislators in Georgia to try to pass a law decreeing that any restaurant that offered iced tea on the menu had to offer sweet tea.
God rested on the seventh day, but early in the morning,
before the sun strained into the Southern sky,
she made sweet tea from scratch. She boiled the water
in a black kettle, put in the orange pekoe bags
and let them stand as the water perked, and then
she did what gods know what to do: she heaped in the Dixie
Crystal sugar while the brew was still warm as the day.
- From "Sweet Tea", by John Lane
Step 1: Boil water, add tea, steep.
Some people have special iced-tea makers -- one of my going-away-to-college gifts from an aunt was an iced-tea maker just so that I could make sweet tea without even having to walk to the kitchen. For much of my first two years there, I carried a bottle of homemade high-octane sweet tea with me to class, instead of coffee. Double strong, double sweet, it was dangerous stuff.
You could use a coffeepot if you're desperate and don't mind your tea tasting like burnt coffee. You could use a teakettle and a good pitcher. Or you could use a big pot; that's what I do, these days, since I don't have the right kind of pitcher.
Boil the water, then turn off the heat and add the bags of tea.
For tea, my grandmothers use Lipton or Luzianne, the big iced-tea bags for making several quarts at a time. One of my grandmothers adds a small bag or two of Constant Comment. For the ~3 quarts of sweet tea I made yesterday, I used two big Lipton iced-tea bags, two small bags of roasted chicory (herbal) tea, and one bag of barley tea from the Korean market up the street. (Not "authentic", but very tasty in a toasted-grain kinda way.) Adding a bag of some kind of spicy chai also works well.
I brew mine a bit stronger than the instructions call for, 10 minutes or so.