Theres a tutorial on multitexturing on gametutorials.com

By the way, in quake3 the technique used is rather just create a new poly with a "hole" texture on it, the effect is great and probably faster than rendering to a texture in real time.

It would be rather complex and slow to use multitexturing for bullet-holes and other decal-style effects. Multitexturing is usually used to apply environment maps over the top of other surfaces, per-pixel lighting and multi-layers polygons. However, that said, Multitexturing is an ideal way to do large-decals ie, where only one decal is covering a polygon.

Anyway -
1. You need a card that supports multitexturing (Basically almost any 3d card these days)
2. You need the glext.h file
3. You need to bind the functions for
i. active (client?) texture
ii. multi texturing coordanite

4. For each texture unit you want
i. Set the active texture unit
ii. Enable texturing for that unit
iii. Bind a texture to that unit

5. For each vertex you produce, specify a set of coordinates for each texture unit.

You''re confused. multi-texturing is applying more than 1 texture to a single piece of geometry. what you''re talking about are decals, which are seperate pieces of geometry (usually just a planar square) that has an alpha blended texture applied to it and which is offset slightly from the surface you''re putting it on, such as a wall.