When visiting a cemetery, what prayer is said at the grave sight for the deceased?

There is a list of psalms that are said on the thirtieth day from the burial and on the anniversary of the death(=yahrtzeit). Some or all of these may be said when visiting on another occasion. Those in charge of the cemetery should have a prayer-book with them that includes the bracha that is made on visiting a cemetery after having not been there for thirty days or more.