http://www.the303.org/tutorials/gold_sprite.htm
Id like to share two long GoldSrc custom map asset creation series I wrote a while back. Both include example RMF&BSP with sprite gallery and assets.
Map Texture Series:
Basic Texture creation, .WAD packing, and hammer config
Masked Transparent Textures
Additive Textures
Toggled Textures
Animated Textures
Water Textures
Scrolling Textures
2D SkyBoxes
Detail Overlay
Batch Conversion
Sprite Series:
Basic Sprites and Orientation Types
Additive Sprites
IndexAlpha Sprites
Masked Transparent Sprites
Animated Sprites
Beam Sprites
I am also in the process of working on modelling for goldsrc series.