Yea I've looked at the cheatengine forums so I have a basic idea of how people use it but I actually have not tried it myself.Cheat engine by itself can't do anything. You need to find the memory addresses (preferably static pointers) that the game uses to store its stuff, then use either scripts or hotkeys to manipulate them. For Dead Space, I have the 3rd person camera parameters all set up in a table and am using hotkeys to basically force it to move around rather than just looking at my character. Basically a free camera. I would have no idea how to do that in Tomb Raider though, as it's probably coded much differently. I do want to poke around in taht game a bit once I get better at CE. I've been using it for almost a year now and I'm still a n00b Comes in handy though when you just wanna take screenshots, as it's pretty easy to find your health and give yourself god mode.
Also, how do you get such a narrow FOV in BF3?
For BF3 I used venice fx to remove the weapon models on the screen. You can then use any gun with a scope to zoom in and get that low fov.