Back to India today, to talk about this question from the box!: I loved your post on Hanuman and I was wondering if you could do a post on another, much less well-known Vishnu devotee: Narada. Your wish is our command!
Narada definitely is less well-known than Hanuman, which I think may be partly because he's just not as flashy as a magical monkey who sometimes leaps across the ocean in a single bound. Instead, he is one of the most highly-respected and famously wise of all Hindu sages, who was looked to by kings, other sages, and even gods for spiritual guidance, and who often appears in the midst of various myths to dispense advice in the nick of time (and also, often, when irritated people don't want it but still need it regardless of their crankiness).
He is one of the most famous devotees of Vishnu, occasionally even acting as counselor to the gods, and like his divine patron is wise and benevolent but also occasionally demonstrates a wicked sense of humor. Narada was mortal, but had in his previous life been one of the gandharva, beautiful supernatural beings who perform songs of praise and carry messages for the gods; he was cursed with humanity after choosing to perform a worshipful song to a mere demigod instead of to Vishnu, who thereafter sent him to become a mortal. His origins are always thinly veiled, however; his family recognized his connection to divinity and he was given to the priesthood of Vishnu at a young age, and his former life as a celestial musician is echoed in his mastery of the veena (which, depending on the region, is sometimes said to have been invented by him) and his status as the most skilled mortal musician of his lifetime.
Narada's career begins when he is a young man, and leaves the company of the priests of Vishnu to wander the forest alone, performing penance and seeking the ultimate truth of the universe. He meditated with such determination and devotion that Vishnu took notice of him, and appeared before him in his full and most glorious of forms, an overwhelming display of glory and beauty that no mortal could bear for long. Vishnu informed Narada that he would never see him in his full glory again until after his death, which was part of his punishment of being mortal; although this turned out to be true, Vishnu did eventually relent and give Narada back his spiritual powers after death, at which point he became considered a servant or even avatar of Vishnu himself, one who has his own temples and devotees.
Narada, like many other divine sages in various cultures' mythologies, usually knows more about what's going on than anyone else does, which results in him doing things that seem to make no sense or appear to be unfair or even evil. Of course, they only look that way because no one else has any idea what he's up to - he may occasionally be more than a little mischievous, but he's not downright harmful. For example, he intentionally told Krishna's father Vasudeva that an innocent family of allies were plotting against him, an outright lie, which resulted in Vasudeva capturing, imprisoning, torturing and eventually killing them. They were understandably pretty upset about this, but Narada told this lie not because he wanted them to suffer, but because only he had the secret knowledge that they were actually deities who had been cursed to be born mortal, and that they could not return to their divine forms until they had been tortured and killed in this manner.
Krishna, who is of course one of the avatars of Vishnu, is also especially fond of Narada, whom he considers perhaps the most pious of all his devotees, and who he turns to for advice in several instances. In each case, Narada counsels Krishna, who is somewhat famous for his temper and propensity for mischief, to employ patience, kindness and love toward others, staving off the possibility of war and conflict with various factions.
Of course, a lot of Narada's life is about atoning for past sins and not getting too full of himself, and in spite of being super fond of him, Vishnu also enjoys punking him to remind him not to get too proud of himself. In one instance, Narada, correctly surmising that he was Vishnu's favorite, point-blank asked him to tell him that this was so; Vishnu responded by instead claiming that a random mortal farmer was his favorite devotee, which immediately offended and confused Narada. He decided to stalk the farmer, lurking in and around his house and fields in an attempt to figure out what made him so special, but succeeded in learning only that the farmer worked all day and prayed to Vishnu once before leaving and once before going to bed.
Because he wasn't quite done pushing his luck, Narada then went back to Vishnu and demanded an explanation for why this random dude who didn't even pray a fraction as often as himself was his favorite. Vishnu told him he'd explain only if he put a large earthen pot of water on his head and walked around with it all day, and managed not to spill even a single drop of water. Narada successfully did so, but upon returning, Vishnu asked him how many times he had prayed to him that day; Narada was forced to admit that he hadn't prayed at all, since he was using all his concentration to succeed at the task, and then Vishnu informed him that he was only impressed by people who could go about their reponsibilities and be devout at the same time, rather than choosing one or the other.
Look at Vishnu back there. He's so pleased with himself. Also hilarious is the story in which Narada becomes too proud of his musical expertise, and Vishnu responds by taking him into the forest, showing him a group of suffering and deformed women, and then explaining that these are the goddesses of music and Narada's playing is so terrible that he's actually killing them with it.
Narada's doings are generally morality tales; he appears as the wise counselor when his advice is appropriate and illuminates things that the audience should learn, but he is also not infallible and soemtimes has to be shown to have failings, so that the audience can also be reminded that even the wisest of sages are not immune to pride, foolishness, or plain old ineptitude.
It would take forever to describe all of Narada's stints as divine advisor to the stars, but they include advising other sages who falter in their duties, helping kings seek blessings for their kingdoms, and even visiting the gods to ensure their religious devotion is still strong in spite of their great powers. The messages of most Narada stories is that it doesn't matter how powerful and holy someone is - they can always strive to be better, and pride in their prowess never does anything but get in the way.
When you're out there being the best Sage you can be, remember the tales of Narada, dear young Heroes. Pride has been the downfall of many a divine adventurer!