Tips on creating emissive textures for headlights and such?

I just wanted to know what techniques you guys use to create emissive textures for headlights, taillights, and such. I've tried to render the reflector in Blender and 3ds max as if it was being hit with light from the 'bulb'. I thought this would work the best but when in game it just doesn't seem to look the same. If you guys use any other methods i'd love to know because creating emissive textures is killing me. Thanks.