(1) Relationship between Dharma, Artha, Kama and Moksha Human life is consumed in chasing materialism (Artha) and sense pleasures (Kama). Ramayana makes it clear that these two pursuits should never be at the cost of Dharma (righteousness). In withholding dharma, both artha and Kama can be and must be sacrificed. The ultimate goal of life is Moksha (liberation) and it can be attained only by relinquishing Artha and Kama and by strictly following a life of Dharma.
(2) The importance of one man being wedded to only one wife
During Ramayana period, polygamy was quite prevalent and it was quite an acceptable social norm for kings to marry many women. Rama's own father Dasaratha was wedded to 3 wives (queens) and he had innumerable concubines at his palace. In a stark contrast to his father, Rama remained wedded and staunchly loyal to his only wife Sita. With this qualification, he held his head high as the greatest king ever ruled in Bharat (India). He set example for future generations of men as to what constitutes a sterling quality for the respectability of a man in society.
(3) Adherence to truth and the need to honor one's word
When Rama was a young boy, the love and affection his father Dasarata had on him was immense. He would never like to be separated from his son. But when he had promised to offer whatever help that the visiting Sage Viswamitra asked for and when the sage requested for Rama's help to fight the demons at the forest, Dasarata was terribly shocked. But still, he agreed to part with Rama, to honor his promise. Later in time, when his third wife Kaikeyi wanted the throne of Ayodhya for her own son Bharata and wanted Rama to be sent in exile to the forest, it was nothing short of a deathly blow to Dasarata. But still, he could never use his kingly authority to veto her request, because of the promise he had made long ago to Kaikeyi, to grant her two boons whenever she chose to ask.
(4) Respecting father's word of Honor
Just on the previous night to Rama's crowning ceremony, Kaikeyi made use of her boons not only to deny Rama his rightful ascend to the kingdom, but also to send him in exile to the forest. Rama, as a kshatriya (a person belonging to ruler/ warrior class), had every right to question such an injustice meted out to him and he was in not really duty-bound to honor his father's unjust promises. But true to his greatness, Rama, with utter detachment and without even a trace of disappointment reflecting on his face, conceded to both the demands. For him, "pitru vakya paripalanam" (honoring his father's words) was one of the highest dharmas.
(5) The futility of listening to vicious counseling:
Kaikeyi, an essentially good natured woman, meekly allowed her very loyal maid servant Mandara to brain-wash her into demanding these two atrocious boons from Dasarata. Though she was not enthusiastic in the beginning, she gradually allowed Mandara's venomous words to poison her mind. Did she gain anything finally by asking these boons? No. She lost her beloved husband Dasarata who died very soon, on account of the shock and the pain of separation from his beloved son Rama. Bharata, Kaikeyi's son, for whom she obtained the very kingdom, reprimanded her for her atrocious act and he never ever took charge of the kingdom as a King. Now see a contrast: Upon hearing the developments, Lakshmana, the most beloved brother of Rama, who was by nature short tempered, like a true Kshatriya, got instantly flared up. He could not just tolerate the injustice meted out to Rama. He wanted Rama to fight for his rights; he wanted to proceed and fight with his father and imprison Kaikeyi. But the ever sober Rama, never heeded to his counsel. He pacified Lakshmana with soothing words, pointing out the need for adhering to dharma. The effect of Rama's counseling not only pacified Lakshmana, but also gave him a steely resolution to relinquish his own comforts of the palace to...