Hi Peter, In MOST of cases, if you want to express that you WANT TO DO SOMETHING, they mean exactly the same thing. We would be splitting hairs to tell the subtle difference between them, (haha...hair was so thin and so fine that it would be a waste of time to try to split it.) 我想+ verb = 我要+ verb =我想要+ verb 我想吃苹果=我要吃苹果=我想要吃苹果 they mean the same thing and they are interchangeble. Keep in mind that they are NOT interchangeble if they are following by a noun, 我想苹果 ≠ 我要苹果 我想苹果（in most of cases it doesn't make any sense） 我要苹果（you say this to response the question"Which would you like to eat? an apple or an orange"） 我想你≠ 我要你（我想要你） 我想你： i miss you 我要你=我想要你： i want to have a sex with you (Be careful to use them:) )

for the meaning "希望，打算" they are same 。 想： 1思索think（我想她刚才那句话的意思）；　 2推测suppose（我想她不会回来了）　； 3怀念，惦记miss （你走后，我会想你的） 要： 1索取demand（我要你向借我的那本书）; 2应该 必须must need（你要认真听讲 ）； 3请求ask for（我要你给我讲故事）

我要 is stronger than 我想. For eg. 我要看电视（I want to watch TV）the demand is very direct and forceful 我想看电视（I'd like to watch TV）It's only a wish,you needn't have to obey it I hope this can help you

我想 {指心里有这个意思要怎么样 处于想法阶段而已 } 我要 {指心里下定决心要做了 则是要准备付诸于行动了 } 比如 我想抢银行 我要抢银行 我想means you just have this thoughts but we have no idea whether you will take action or not我要means you have made up your mind

我想=我想要 wo xiang=wo xiang yao,means i want, 我要 wo yao,means i will or i am going to ...