Green tea can help very slightly. The only studies done on green tea showed that if you drink 4 cups per day every day, you can lose about 8 pounds in a year. That's not a lot to count on. Also, the studies showed the effect with real green tea, not capsules. So it's more myth than truth. However, lots of people find that drinking green tea helps satisfy the appetite so you might eat less. It's definitely good for you, green tea is loaded with antioxidants. But you should probably ditch the capsules and drink the real thing to get the most benefit.
I read in Women's World, I believe, that if you take green tea capsules to take them in the morning before eating anything and drink a full glass of water with them. It said that they absorb better that way. I've been doing the green tea that way, and while I won't say I've really noticed a difference, it does give me a big boost first thing in the morning!
I don't know about the green tea part, but it seems to me that if you are drinking a significant amount of water with either a capsule or tea bag, you will fill yourself up faster and not feel as hungry. That alone should help slightly with weight loss.
I have heard about green tea's benefits, so I try to drink that at work whenever I am cold and need something to warm me up. It helps that I'm not a daily coffee drinker anyway!