'Psycho' was first of the horror genre to demonstrate a psychotic killer and within this film made its own conventions and sculpted this genre for the future. The only film that has had a bigger impact on the genre is 'Halloween'.
This is a link to the IMDb page for 'Psycho'
In the opening to 'Psycho' Hitchcock uses an establishing shot of a city and slowly approaches a window of a flat. He does this by cutting many shots instead of one full fluid motion. When we get to the window the camera goes inside to shoot a man and a woman ('scream queen') and final girl. The woman is in her bra and the man is shirtless, this signifies that they have just had sex.
We can learn from this because in our production we enter a house and we want to signify that our 'scream queen' and male have just had sex, we need to carefully craft this as we are NOT including nudity but at the same we intend to make it clear to the audience that the girl is sexually active. This links to key slasher conventions saying that if a girl is sexually active she needs to be slaughtered.