Certain features of saluting in the Marine Corps carry Marine Corps custom specifically. For example: Marine Corps usage has it that a greeting be exchanged when saluting a person. When saluting an officer, the Marine might say, "Good Morning, Sir," or "Good Evening, Sir," as appropriate. The officer in returning the salute would say, "Good Morning, Sergeant (Private, Corporal, Lieutenant, as appropriate.)"
Marines in uniform salute officers (or senior officers), even if that officer is in civilian clothes (assuming the Marine recognizes the individual as an officer). Conversely, it's not considered appropriate for a Marine in civilian clothes to initiate a salute to an officer (or senior officer), even if that officer is in uniform.
During the playing of the National Anthem, at morning and evening colors, and at funerals, if in civilian dress, Marines uncover and hold the hat over the left breast at such times as those in uniform salute.
There are many other customs which have significance in the life of a Marine. A few of the notable ones are listed here.
Boarding a small boat or entering a car. When boarding a small boat or entering a car, Juniors enter first and take up the seats or the space beginning forward, leaving the most desirable seat for the senior. Seniors enter last and leave first.
Marines' Hymn. Whenever the Marines' Hymn is played or sung, all Marines rise to their feet and remain standing during the rendition of the music.
Serenading the Commandant. Commencing with the last New Year's Day of the Civil War, on the morning of 1 January of each year the Marine Band serenades the Commandant of the Marine Corps at his quarters and received hot buttered rum and breakfast in return.
Wetting Down Parties. Whenever an officer is promoted, he customarily holds a "wetting-down party." At this time the new commission is said to be "wet down." When several officers are promoted at the same time, they frequently have a single wetting-down party.
Wishes of Commanding Officer. When the commanding officer of a Marines says, "I wish" or "I desire," these expressions have the force of a direct order and should be acted upon as if he had given a direct order.
Looking Out for Your Men. One feature which has made the Marine Corps such a respected organization is the custom of Marine leaders looking out for their men. A Marine leader makes sure his men are comfortably clothed, housed, and justly treated. For example, in the field a Marine officer takes position in the mess line after all the enlisted men in order to insure all men get their food. A Marine leader never leaves a wounded or dead Marine on the battlefield to fall into the hands of the enemy.
Being a Marine.But the most outstanding custom in the Marine Corps is simply "being a Marine" and all that it implies. Call it morale, call it esprit de corps, call it what you will--it is that pride which sets a United States Marine apart from the men of other armed services. It is not taught in manuals, yet it is the most impressive lesson a recruit learns in boot camp. It is not tangible, yet it has won fights against material odds. Perhaps it has best been defined by Senator Paul H. Douglas:
"Those of us who have had the priviledge of serving in the Marine Corps value our experience as among the most precious of our lives. The fellowship of shared hardships and dangers in a worthy cause creates a close bond of comradeship. It is the basic reason for the cohesiveness of Marines and for the pride we have in our corps and our loyalty to each other."
A Marine is proud of his Corps and believes it to be second to none. He is loyal to his comrades and to the Marine Corps, adhering always to the motto Semper Fidelis (Always Faithful).
Above Information from the Marine Corps Historical Reference Series, 1963, Courtesy of the United States Marine Corps