Spain's King Juan Carlos lets his son and heir Felipe in on the secrets in ten confidential letters which have just been published for the first time. ( dpa )
"You need to appear animated even when you are tired; kind even when you don't feel like it; attentive even when you are not interested; helpful even when it takes an effort."
The advice is included in one of the letters published by journalist and royalty expert Jose Garcia Abad in his book El Principe y el Rey (The Prince and the King).
Juan Carlos, now 70, wrote the letters in 1984 and 1985 when the then 16-year-old Felipe was finishing school in Canada.
The letters are a "document of extraordinary political value" and a "treasure for historians," Garcia Abad writes in the daily El Mundo, which published advance excerpts of them.
Felipe would have it easier than his father, who became king by the will of dictator Francisco Franco after the 1931-36 Second Republic, the 1936-39 Civil War and Franco's subsequent rule, which ended with his death in 1975, Juan Carlos observes in the letters.
"I have had to stand snubs and contempt, incomprehension and annoyances that you, thank God, have not known," writes the king who was first looked down upon as the dictator's puppet, and only won a widespread popularity by thwarting a coup attempt in 1981.
Yet Felipe, who will need to consolidate the monarchy, is expected to face different kinds of obstacles as king.
He could face a more hostile media environment and closer scrutiny, the first signs of which were visible in 2007, when a sexual caricature on him sparked a scandal and media treatment of the royal family generally grew bolder, analysts point out.
"We all are a bit slaves" of the media, which can "elevate or pull down a person or an institution," Juan Carlos writes to his son, advising him that "the press needs to be respected, but it is also necessary to make it respect you."
"All that you do and say will be analyzed in a special manner," the king cautions, also warning that scandals "will be in you... more scandalous than in another boy of the same age."
Royals can no longer expect "rights and privileges" only by right of birth, stresses Juan Carlos, who has been quoted as saying that he needs to "earn his throne every day."
A king needs to be sympathetic without coming too close to his subjects, prudent without appearing indifferent or evasive, and proud of who he is without appearing snotty, the monarch writes.
Felipe will "shake hands with everyone, but when you reach out the hand, it should be the hand of a prince or king."
"You need to appear natural, but not vulgar; cultivated and aware of problems, but not pedantic or conceited," Juan Carlos further advises his son.
The letters leave no doubt that Spain's king sees himself as exercising real power as a behind-the-scenes political intermediary and as the official head of the armed forces, though many constitutional experts would question such an interpretation.
Power, however, must not exercised too openly, the king tells the crown prince. A king needs to "listen a lot" and to "speak with a sense of proportion."
"Knowing how to be quiet is as difficult as knowing how to talk," Juan Carlos adds.
In the public sphere, the golden rule is "to talk a lot, but prudently and without making important affirmations," he writes.
The letters reflect Juan Carlos' subtle understanding of his role, as well as the affectionate relationship between father and son, Garcia Abad observes.
"You are missed and loved a lot," the king wrote to the young prince, signing it "Father."