Watson tells the story in the first person we know this because the story is told by him and his diary also this has already happened making this in the past tense, the events happen in chronological order. Watson describes everything very slowly and in detail up until they chase after the hound, then everything happens very quickly after this. Conan Doyle uses clever wording in his sentences for example: a key turned in the lock and as he passed in there was a curious scuffling from within this creates tension because it makes you fearful of what is in the shadows of the room.
This makes you want to read on to find out what happens and what creature lurks inside the abyss. Conan Doyle makes you panic when he introduces the sea of fog gliding across the Grimpen Mire. This causes tension because if sir Henry does not get to them the hound will get him then when the hound leaps out of the fog with burning blue teeth it makes you jump up in your seat. This dissipates the tension and everything turns into adrenaline to kill the hound.
You know something scary is going to happen when they cock there pistols ready to shoot what ever comes at them earthly or demonic. Hist cried Holmes and I heard the sharp click of a cocking pistol this shows that they are ready for anything and this builds tension because your eagerly anticipating whatever is going to come out of the fog. Conan Doyle creates tension by making sure that Holmes does not tell lestrade and Watson anything this makes them very annoyed but because of this it creates a lot of suspense and tension in the reader because you do not know what is going on.
The Grimpen Mire is described as a dangerous creature crawling across the mire and towards the house and this creates a threatening atmosphere because unless sir Henry gets to them in time then Holmes plans could be thrown into disarray and the hound could kill sir Henry so this creates a tense atmosphere. The Grimpen Mire is described as a huge morass of foul slime filled with bones. Protected by the foul smell of the swamp, which gives off a very sinister smell, which gives it a sinister feel and how cruel Stapleton was. Stapleton had obviously gone slightly mad in his desperate attempts to kill members of the Baskerville bloodline.
In conclusion Conan Doyle creates tension by keeping his cards close to his chest up until the very last few moments and this is how he develops tension. Also by describing the scenes and introducing the sinister fog it makes the scene scarier. The tensest bit is when you are waiting for the hound after sir Henry has passed and there are a few heart pounding seconds waiting for the creature. I think that Conan Doyles choice of language and the way he sets out the environment is how he creates tension and that this is why it is so tense in chapter 14 of the Hound of the Baskervilles.