The Evad3rs have released an updated version of the Evasi0n jailbreak utility that improves device boot times following jailbreak.
What's New in Version 1.5:
- Improved boot-up time.
- Updated included Cydia package list.
Here are the Evasi0n Download Links. Also You can find detailed instructions on how to jailbreak your particular device.
If you are planning to update your device to iOS 6.1.2 you should make a backup and properly restore your device in iTunes. Do NOT use the over-the-air update.