On arriving at Stoke Moran, Holmes, determining which wing the family resides in, first examines all the windows from the outside and is able to determine where Miss Stoner used to sleep, as well as the location of her sister's and Dr. Roylott's bedrooms. He then has Miss Stoner go to her room and bar her shutters. He tries to tries to force them open, but is unsuccessful. Therefore, he heads inside.
Inside, he goes directly into the bedroom Miss Stoner is now occupying, which is her sister's old room. He looks all around it, and Watson supplies the reader with the details of the room. Holmes then sits in a chair and appears to be thinking. He notes that a bell pull, which is what the occupant of the room would pull to call a servant, appears newer than the rest of the items he sees. Miss Stoner says it is newer and that it communicates with the housekeeper's room. Holmes looks all over the floor and the woodwork with his magnifying glass, and finally pulls the bell rope. When he does so he, he notices is it a "dummy," meaning it doesn't really work, which he comments on as very curious.
We see by his actions how very methodical and careful Holmes is. No detail seems to escape his notice.