If you don't know whether or not your device can be jailbroken or your iPhone is able to be unlocked or not, f0recast is the tool for you. Its specially for those who are new to the jailbreaking scene. Good news is that the developer, iH8sn0w has updated f0recast to version 1.3 and it now supports the current jailbreak state.
Download f0recast 1.3 for Windows
Download f0recast 1.3 for Mac