Observation of a person can reveal much personal history

The history of people are engraved in their bodies and reflected in their clothes. When first introduced to a person, you can tell much about his/her past history and present profession. Such a precise first impression is not obvious. You have to know where to look and what to look for.

Always look at the hands first, Watson. Then cuffs, trouser-knees, and boots. Very curious knuckles which can only be explained by the mode of progression observed by --- [CREE].
By a man's finger-nails, by his coat-sleeve, by his boots, by his trouser-knees, by the callosities of his fore-finger and thumb, by his expression, by his shirt-cuffs - by each of these things a man's calling is plainly revealed [STUD].
I demonstrated to Watson by describing his recent personal history when I deduced from his dress that he had spent the day at his club [HOUN]. The most revealing part of a person is, of course, the face. "Reading faces" is another part of that literacy required by a detective.
The features are given to man as the means by which he shall express his emotions, and yours are faithful servants [CARD].
My eyes have been trained to examine faces and not their trimmings. It is the first quality of a criminal investigator that he can see through a disguise [HOUN].
This would appear obvious. However, it is only obvious after you have revealed what you know:
You know a conjurer gets no credit when once he has explained his trick: and if I show you too much my method of working, you will come to the conclusion that I am a very ordinary individual after all [STUD].
However, since there is enough mystery in the world without creating that false mystery of mystique, it has always been my habit to hide none of my methods, either from my friends or from anyone who might take an intelligent interest in them [REIG]. The small price I pay for this candour is to be greeted - after revealing my method - with remarks like I thought at first that you had done something clever, but I see that there was nothing in it after all [REDH] and For a moment I thought you had done something clever [NAVA].