因为问一个美国同事一首歌，我说我很喜欢这个曲调，但是不知道是什么歌。然后，他就说他可以找到CD.我不知道他是有CD，让我copy一下;还是会帮我买一张CD.
所以，我就想，他给我CD的时候该怎么办？
是不是先问多少钱，然后照价给钱，还是要加10%给钱？

I don't know how to deal with this thing with an American guy. But I would feel uncomfortable if I were your American colleague.

ask him about the title of CD and buy it on internet yourself, or find in local library. It's really uncomfortable to copy from his CD, you know. Some of them are really aware of copy right.

问他own他多少钱然后就给那个价钱就好了。。你如果觉得不好意思再送个小礼物以示感谢吧。。加消费好像很怪。。。

不用吧，同事之间不存在小费。就像楼上题的，表示感谢给个小礼物就可以拉，其实都是同事，口头感谢应该就好啦。