If you have firmware that hasnt fixed the TIFF exploit, just go to jailbreakme.com in your iphones safari, it wil jailbreak it, duh lol.
After it has finished, go to sources in the bottom right, click edit, then click add, add
hppt://i.unlock.no, and click ok.
Then once its refreshed, go to install and go down to unlocking tools, install the ones that you like.
If you have more recent firmware, pm me and ill explain the process of downgrading and how to jaiulbreak the new firmware