Step 1: Download iOS 4.3.5 and iOS 4.3.4 (required by this version of Redsn0w) firmware file for your device from the links given at the end

Step 2: Download Redsn0w 0.9.8b4 for Windows or Mac. Also make sure you are running the latest version of iTunes, which is version 10.4

Step 3: Now start Redsn0w, browse for the iOS 4.3.4 firmware file (NOT the 4.3.5) that you downloaded in Step 1 and point it towards Redsn0w

How to activate your device without UDID account

1: Download Firmware I OS 5 Beta 5 for your respective device

2: Download iTunes 10.5 Beta 5 

3: Jailbreak I OS 5 Beta 5 Using Redsn0w 0.9.8b5