Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
Which hand and finger should the ring be worn:
It is preferable to wear it on the right hand.
'Ali bin Abi Taalib Radiyallahu 'Anhu says: "Rasulullah (Sallallahu Alayhi Wasallam) wore his ring in the right hand". (Shamail Tirmidhi)
Imam Nawawi says that it is Sunnah and according to Ijmaa'(concensus) to wear the ring on the smallest finger and to wear it on any other finger is disliked.
Where should the stone be facing:
It is stated in the 'Badh-lul-Majhud' and 'Mirqaatus-Su'ud' that it is more correct to wear the top part of the ring facing the inside (towards the palms). This has also been stated in many narrations. Also, Allamah Munaawi says that this is best because it protects the stone and saves one from pride and high mindedness.
For more information please refer to these links:http://www.inter-islam.org/hadeeth/st11.htmhttp://www.inter-islam.org/hadeeth/st12.htm
And Only Allah Ta’ala Knows Best.