How would one go about making a pokemon hack tool?

[spiteanims]

There's a hell of a lot of documentation on rom hack tools, but so far I haven't been able to find anything regarding how to make hack tools. I've been experimenting with C/C++ and I have no idea how to go about it. Any ideas? 

[theSLAYER]

Start with a small ROM hack tool. Maybe perform something simple, like change a starter or an encounter or something.
Then proceed from there.