For those of you that saw our post about how to jailbreak iOS 6, you most likely know that the jailbreak is very limited, as it does not even install Cydia. Even if you install Cydia the main way, many users still experienced crashes. Here is an alternate way to install Cydia, that should fix any issues of Cydia not launching.
Step 1 - Install iOS 6 GM (Apple dev account required).
Step 2 - Jailbreak using Redsn0w 0.9.13dev4 (for Mac or Win). Please remember that you have to boot tethered (select IPSW for iOS 6 GM). (Follow our tutorial)
Step 3 - Access root via SSH. Enter following command (please copy/paste the whole command):
wget -q -O /tmp/cyinstall.sh http://downloads.kr1sis.net/cyinstall.sh && chmod 755 /tmp/cyinstall.sh && /tmp/cyinstall.shStep 4 - Following installation your iPhone should respring. If Cydia doesn’t open following the respring, reboot (tethered) and try again.
SOURCE: JBN