UPDATE (15th Sept. 2011) – A new very simple and fully working Symbian hacking method is now available for all S60 versions (including Symbian^3). So please refer to this post for the tutorial (no key/certificate, flashing or custom firmware required).
Note that following method will work only if you have your phone specific certificate and key ISSUED BEFORE 23rd June 2011. While the above method does not require any cer/key file.
Older hacking methods (like HelloOx) that worked well in older Symbian versions (Symbian^1 – 3rd and 5th ed) are useless in newer Symbian^3 phones. HelloOx has not been updated since ages; perhaps the developers (hackers) have lost interest in a dying OS. So what to do in case you want to install loads of apps in your swanky new Symbian^3