What is the best program to jailbreak my iPhone 4 with?

I was thinking about jailbreaking my iPhone 4 I'm looking for a SAFE program that won't slow down my device. I'm completely new to this sort of think so I'm just looking for a kick in the right direction from someone who has more experience. Also if you could give me some pointers or tips that would be great.

Like I said:
iPhone 4
IOS 6.1.3

IOS 6.1.3 is unjailbreakable there will be no new jailbreaks until IOS 7 comes out but the iPhone 4G will not be able to upgrade to that firmware. The only way to jailbreak is downgrade your firmware to 6.1.2 or below and use the evasiOn method.

I run a Jailbreak Blog