I drink green tea everyday - I'm not sure if the tea itself has anything to do with my weight loss, but having something flavored (I'm so sick of just water and I hate diet drinks) has helped a lot.
, I got a cast iron (Tetsubin) for Christmas last year. I did some research and found that for green tea, the "correct" way to brew it (at least this is a good starting point) is to use 2.3 grams of loose leaf green tea (about 2-3 teaspoons) for every 8 oz. of water. Heat the water to just below boiling (you can bring the water to a boil & let it sit for 2-3 minutes before using it). Then brew the tea for 2-3 minutes, any longer than that and you're risking making the tea bitter. Also, I swish hot water in the tea pot to warm the iron first, supposedly it makes the tea better. Also, there are tons of varieties of green tea, and some can be brewed at higher temps, or for longer -- so just have fun experimenting!
I had no idea how to use loose leaf tea - but now I'm 100% addicted to it. I found a great website that has sampler teas so you can taste all the different kinds. I love green and white tea now. And they are definitely good for you!
So, even if they don't directly aid in weight loss (not sure if they do or don't) but they are healthy & definitely help with the boredom of drinking plain old water, especially if you dislike diet drinks like I do.