First-person narration, according to authors such as Stephen King -- and in famous examples such as Anne Rice's "Interview with the Vampire" -- is usually a first choice for both new and established authors. It has the strengths of accessibility, simplicity and directness; its difficulties include limited character description, especially self-description and the constrained plot interaction that the first-person point-of-view imposes.
Strengths of First Person
Matthew Lee Adams, a paranormal-fantasy author, suggests that first-person is accessible because the author uses his voice for narration; the creator has an immediate connection to the creation. This imparts an understanding of the character that might otherwise have to be imagined, and it gives a strong starting point for the story. "Once upon a time" done in the author's own voice is simple and direct. Simplicity and directness, plus accessibility, are automatic.
Two First-Persons, One Author
This directness makes the author's job so easy he often repeats it. Rice's "Interview with the Vampire" uses the character Louis as its first-person narrator; it ran itself off as a novel so speedily that she duplicated the feat with "The Vampire Lestat," this time using Lestat as the first-person protagonist. Her joy in the writing, and the interest the Lestat series spawned for readers, testifies to her success with both characters.
Limitations of First-Person
King, on the other hand, definitely favors third-person narratives, preferring as he does to work on a large canvas; his book "On Writing" discusses the different points-of-view in his epic novel "The Stand." King prefers third person as it allows him to move through a number of sub-plots and different narrative threads with ease. A first-person narration is limited to a single story thread; also, descriptions of the narrator or other characters can be problematic if the author is stuck with one pair of eyes.
A Clear Voice, But Limited
First-person narration is definitely easier for many, but it has its pitfalls; even a masterly author like Charles Dickens, who began "Bleak House" with Esther Summerson as first-person narrator, occasionally forgets to keep the book in Esther's voice. Limited plot interaction and description aside, however, first-person narration decidedly gives authors direct access to a clear literary voice.