Buy a wifi antenna the longer the range the better. Some can reach up to 20 km. If buy you from some chinese in ebay they even include a cd that will enable you to automatically hack weak wifi systems and you will able to connect even it has passwords.
lol .... why would you hack a wi-fi???
I never understood people who hack wi-fi's to use them!
You hack a wi-fi if you need someone else password .... not to use his wi-fi ... because if you hack a bad ass mother fucker's wi-fi then he will hack your passwords!