We all know of the Clever 'Claw, the Sleazy Slyth, the Hardy Huff and the Grand Gryff. But why do the Houses of Hogwarts line up like that? The reason for that is found in the caste system.
Society is commonly described in terms of four castes: The Rulers, the Warriors, the Priests/Scholars and the Workers.
The Rulers are of those that claim to rule over all else. They are generally ambitious and power-hungry. You will note that these are also typical Slyth traits. Salazar Slytherin was without doubt of the Ruler caste.
They'll be department heads, managers, bankers and traders.
The Warriors, whose task was to protect land and lord, are generally brave, stubborn and fiery, as are Gryffindors. Hence, 'Gryffs rush in where others fear to tread'. Godric Gryffindor was clearly a Warrior.
Look among the soldiers, policemen and firefighters.
Priests and Scholars. Wisdom, intelligence, hunger for knowledge. What can be more Ravenclaw than that? Rowena Ravenclaw was a Scholar if there ever was one.
Seek out doctors, teachers, professors and computer programmers.
Workers and Farmers are the salt of the earth, figuratively if not literally. They share traits with Hufflepuffs - industry and equanimity. Helga Hufflepuff was very probably born of Farmers.
They're farmers, factory workers and the rank and file in the industries.