Why aren't you googling this simple question. This has been asked and answered a ton.
Nvm, still gonna answer.
To start with hacking I suggest you start learning C/C++.
So what I suggest you to do is buy/pirate a book. I am currently reading a book called Jumping Into C++, you might wanna check it out.
If not there's alooot of other books out on the internet.
Now for the second step. After you are done learning C++, you need to learn Assemble.
Because If you are going to hack programs/games you need to know how to reverse engineer.
For example when you are going to crack a program that is free for 3 days and then you must buy it. If you know assemble you can just add a JMP to jump over the check if bought using OllyDbg for example.