Hey is there anyone insanley good at halo 3 that wants to help me get my rank up?

I have an Xbox 360 and play Halo 3. I record clips from my played games all the time. When I watch the recorded clips, the cross hairs of my gun never show and are non existent. I see people post videos on youtube of their Halo 3 gameplay and their cross hairs are showing. How do they record their Halo 3 gameplay, showing the cross hairs?

on halo 3 how do i customize a game