Unless you're an experienced hacker, it's pretty unlikely that you'll have the knowledge or tools available to be able to hack someone's phone. There are, however, a number of websites that offer phone hacking services.
SPYFish claims to offer PC software that allows the user to spy on any phone they like. By this, they state that you can enter someone's phone number into the software, and see everything they use their phone for.
SPYFish is supposed to let you look at text messages, call logs, emails, browsing histories, and basically anything else the owner decides to use their phone for.
Ultimately, it's highly doubtful that any software like this will work. In actual fact, I'm pretty certain that it's illegal to spy on someone like that, and would probably constitute stalking.
I'd advise against trying to hack someone's phone as it's not only immoral, it'll also land you in a fair bit of trouble with the authorities.