Example

glActiveTextureARB(GL_TEXTURE0_ARB)
glEnable(GL_TEXTURE)
glBindTexture(texid1)
glActiveTextureARB(GL_TEXTURE1_ARB)
glEnable(GL_TEXTURE)
glBindTexture(texid2)
...

glBegin(GL_QUADS)
glTexCoord2f(0, 0)
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0, 0)
glVertex3f(-5, -5, 0)
...