how can i learn to make a hack for games like my own html or somthing like that?

[kenshin himura(battoasai)]

i want to make my own hacks for like online games i want to know a way to make them or is their a website that will teach me this question kinda needs to be answed soon no rush but if some one could help or like post a link to a website that will guide me step by step.