Many times we've been asked about the wearing of the ring with the "Most Great Name" on it. As to which finger is suggested to wear it on, this is what we have found:
"The giving . . . . . . . . the ring [1] of the Greatest Name is very beautiful. The ring should be worn on the small finger of the right hand."
('Abdu'l-Bahá, Tablets of 'Abdu'l-Bahá v1, p. 178)
Although 'Abdu'l-Bahá has suggested it to be worn on the small finger of the right hand, as most things in the Bahá'í teachings, this is left to the discretion of the believers. Now, as a personal observation, perhaps there was a reason behind this suggestion - we don't know but we are sure there must've been a good reason for Him to do so.
Personally, wearing Baha'i jewelry with this Greatest Name on it serves as a personal reminder that we should life in a prayerful attitude, constantly thinking about God and how we can best serve humanity. Whenever one stares at this Symbol we can be reminded of the purpose of our lives. It's like a pause from what we are doing to re-focus on what really matters and why we are on this earth.
I came across another very beautiful and enlightening quote from one of His Tablets, where 'Abdu'l-Bahá further explains:
In one of His Tablets, 'Abdu'l-Bahá wrote: 'If you seek immunity from the sway of the forces of the contingent world, hang the 'Most Great Name' in your dwelling, wear the ring of the 'Most Great Name' on your finger, place the picture of 'Abdu'l-Bahá in your home and always recite the prayers that I have written. Then you will behold the marvellous effect they produce.
(Compilations, Lights of Guidance, p. 520)
Isn't this beautiful and interesting?