Creating trainers?

I'd like to learn how to make my own trainers (or how to update other trainer for newer TUs) and I'd like to hear from you guys what things I actually need and what things I should keep in mind.

Some information about my Xbox:

MS Kernel is 2.0.16202 right now
Dashlaunch is 3.07
My Xbox has a Falcon board and has RGH (1)

I'd appreciate any help or support

btw: Pardon my horrible English

 

Thanks for the Tut
But I think, a trainer with unlimited ammo can't be made with this, I'm afraid
Anyone else?

 

I thought you need breakpoints for that?