Help with textures

I would need to know how to control the reflection textures have. As I always say, it's not for me, but for a friend, so forgive my ignorance D:
I would really appreciate any info,explanation,link, or whatever.
THX in advance

Give your friend this link, most of the basic mapping question can be answered there:

http://developer.valvesoftware.com/wiki/SDK_Docs

For reflection textures for example look for:

Material System -> Reflective Materials

wow, thx swot. Appreciated