In this new series, I am going to just pick out the highlights of Easier Mystery Play and make some 2-4 minute videos.
The briefing is really important. The briefing is the moment that you introduce the mystery to the characters. It could be literally a person telling them what they need to do, it could be a clue in a book or a body on the floor.
The important thing about the briefing is that it gives the characters their first routes into your mystery. They have to be clear enough that your characters cannot possibly miss them, and I suggest giving about three different ways of starting off. That could be a couple of witnesses or some material evidence. You do not want to put everything on a single clue and then have the players fail to grasp its significance!
If you had a body on the floor, the means of death could wield clues, such as the weapon and evidence of the attack (front of the body or rear?) what is the weapon, how common are they? Another route is the victim, who were they? What were they doing here? Then you have the location of the crime. Were there witnesses? CCTV?
In a fantasy setting the mystery could be as simple as finding a hidden door. You still need something to plant the idea that the door exists. No clues, no mystery, and no door gets found.
Easier Mystery Play is part of a series of GM Advice and Tips books available on DTRPG and Amazon. If you would like to get free solo rules, tips, advice and discounts on new books, you can join my mailing list.