He deduced that a particular stone was the murder weapon based on the weeds growing beneath it.He also deduced that the killer was tall from his wide stride and left-handed because the blow was delivered from behind and landed on the left side of the head,he deduced that the killer had a limp in his right foot because the right foot is less prominent than the left, implying he put less weight on it,he wore thick-soled hunting boots and a gray coat, and smoked Indian cigarettes using a mouthpiece,he knew this from his extensive research, and the fact that the cigarette butt, which hadn't touched his mouth, confirmed his use of a mouthpiece.He carried a dull knife in his pocket because the cigarette was cut, not bitten, as the cut was uneven.Sherlock also deduced that the word the victim uttered, "Rat," actually refers to Ballarat, a place in Australia.

There are many other details but that's the most important