Put the tea bag into the mason jar. I suggest putting your sugar in at this point. I find once the hot water is in the jar, it creates condensation and the sugar can stick to the sides of the jar. Not fun!
Pour hot water into the mason jar. I find filling it halfway is the best. Set your timer for the normal amount of time for the type of tea you're using.
Remove the tea bag, squeezing out excess water.
Throw a bunch of ice cubes into the jar, but don't fill it all the way up yet. This will make it easier to stir without making a mess.
Stir the tea vigorously to allow it to cool down quickly. Once those cubes have dissolved or the tea is cooled down a lot, add more ice. I usually fill it right to the top with ice cubes at this point.