If you don't know how to use cheat engine then I'd suggest you do the tutorial on it and then go to the cheat engine forums and just start hacking and asking questions to gain experience.
There's a thread here that tells you what's server sided and what isn't, so you can use that to see what you can and cannot hack with cheat engine.
If you wanna hack more of the fun stuff in the game you'd probably need to learn about packet sniffers and networking in general; and maybe some programming to be able to create your own tools? I'm not too sure.