Some of the techniques used by Sir Arthur Conan Doyle in The Hound of the Baskervilles include first person narration, foreshadowing, Gothic setting, red herrings, irony, symbolism, and foils. As usual in Sherlock Holmes stories, Dr. Watson is the first person narrator. This allows Doyle to unfold the story in a way that gives the reader glimpses into clues without divulging everything the detective knows. This story is unusual in the Holmes canon in that Watson is on his own for several chapters, representing weeks, without any appearance of Holmes.
Foreshadowing occurs with each of the clues in the mystery, including the warning note, the warning from Miss Stapleton, the howling on the moor, and the suspicious behavior of the Barrymores. Another instance of foreshadowing is the sinking of moor ponies in the Grimpen mire, which foreshadows the ultimate end of Mr. Stapleton.
The book uses a Gothic setting including the lonely, dangerous moor; the dark, foggy night; the isolated mansion; howls heard at night; the legend of the curse of the Baskervilles; and reports of a large creature roaming the moors at night. Doyle uses this setting to add suspense to the novel.
Red herrings are false clues; in this book, the subplot of Seldon, the escaped convict, is a red herring that casts suspicion on the Barrymores. This creates an interesting twist in the story.
Irony occurs when Watson suspects the "man on the Tor" as being involved in the mystery, but he turns out to be Holmes, and when Stapleton, who has spent two years learning the safe ways to travel through the Grimpen mire, ends up being sucked into the mire when he flees from Holmes.
Additionally, the symbolism in the book supports the novel's theme of the forward progress of mankind and the superiority of reason over superstition. Dr. Mortimer's comments in chapter 1 about the form and size of Holmes' skull, for instance, point to the size of his intellect. The legend of the curse of the Baskervilles represents superstition, mythology, and even religion, which Holmes dismantles via reason. And the Neolithic stone huts on the moor represent the dark ages of man's development, which have now been "taken over" by Holmes' superior intelligence.
Finally, Doyle uses at least two foils in the novel. A foil is one character who reflects the nature of another character by providing a significant contrast. Watson is always the quintessential foil to Holmes in that he sees the same clues many times, but fails to deduce their meaning as astutely as Holmes does. Similarly, Sir Henry is a foil to Mr. Stapleton; both are Baskerville heirs, but Sir Henry is kind and worthy, while Stapleton is diabolical and unworthy. Through these and other literary techniques, Sir Arthur Conan Doyle adds interest and suspense to his novel.