a quick way of explaining what you need to do before you are ready to go out. The s's stand for: Shit, Shower, Shave.
for extended version see "4 s's"
Wife: Are you ready to go out for a meal.
Man: No, I just need to do the 3 s's
Wife: Well I won't eat it this time
Shower, Shit and Shave.
I have to do the 3 s's before i go out.