Difference between 要 and 想?

In the lesson about Ordering drinks and Plane tickets, we used: 我要一杯中国茶 = I want to have a cup of cofee 我要买。。。 = I want to buy... However, in Planing a Trip we use: 我想去。。。 = I want to go to... What is the difference between those two words? (想 and 要）, how do we know when to use which?

I'm just learning this like you are, but I thought I'd take a crack at it. I believe that 要 is used when you are making a request for something you want or need, while 想 is used to indicate that you wish to, or have a desire to do something. For example: I want a pound of bananas - use 要: 我要一 斤 香 蕉。 I want to study Chinese – use 想: 我想学汉语。 I think that's right, but someone please correct me if I'm wrong.

Yes DboP nailed it. 想 is not as strong of desire to do something, so you are thinking to do something but you haven't decided. 要 is much more certain and you are pretty sure you want it. Additionally there are a couple differences: 我想一斤香蕉: i MISS a jin of bananas 我要一斤香蕉： i want a jin of bananas compare first one to: 我想吃一斤香蕉： i wish/want to eat a jin of bananas. you see? if 想 is not followed by another verb then it changes meaning "to miss"