Hi Raven, welcome – dynnargh dhis!
There is no formal, set etiquette as far as I’m aware, other than the respect you’d bring to any sacred site. However, my own etiquette would be to approach the stones and walk around them clockwise on entering and then anti-clockwise on leaving. I’d also take some time to sit quietly with the stones and if you touch them, touch them with an open and sincere heart. If there’s any litter, as sadly there can be, do something positive and pick it up to keep the site clean. In that way you’d also be showing some respect and sending out some positive energy. I’ve often sat with lonely stones on the moors, the trouble is that a sheep can often have the comical effect of disturbing your sublime thoughts! Ha ha! Anyway, take care and I hope your visit to the stones, wherever they may be, is meaningful for you.