The title of this post says it all: when does the scene start?
The writer has to know everything. She knows eye color, favorite foods, gun calibre. She knows everything about the story.
For the reader, the writer decides when the tale begins and does so with every subsequent scene. We'll look at openings here.
Does it begin when the character wakes up and loiters over a coffee? Probably not. We write crime and there isn't much crime over coffee.
Now, the character wakes up, makes a coffee, sits down, and addresses the corpse on the floor in a familiar manner: might start a scene.
Character - skip the wake and make part - sits down with a cup of coffee and looks out the kitchen window to see SWAT guys closing in on the house next door. It's the rental property with which our character switched last digits of a house number.
We have a little more here - but is it the start? Doesn't seem like the start of the story, does it? Might be the start of the scene.
Shakespeare starts
Hamlet with Bernie and Frank looking much like the fellow from a morgue file image above. The action has already begun when we meet the characters. Frank has startled Bernie and we begin with Bernie's response: Who's there?
So, what's the rule?
The rule is we start a scene with enough information for the reader to orientate themselves to the action at hand even if the action chain already has been set in motion.
If the first thing that happens is that a bullet hits a fellow waiting for a bus: that's the story opening.
The scene might not start until the detective already out of his car complains to the waiting uniform that the M.E. folks are useless bastards who should already be here. He goes on to say that they haven't responded within two hours of a call in the last three cases he worked.
The Uniform answers that the M.E. on duty - Williams - is a drunk since his wife passed.
We could begin our story about an anti-hero who stumbles onto a problem he alone must solve by introducing him by reputation. The story could be about Williams and when Williams shows up trying to make due despite a massive hangover (pukes when he gets out of the car) we already know why the M.E. is a Nick Cage character style of sleezeball.
Did we open with the M.E. opening the car door and puking ? Could have. Could have back filled the details in conversation "about" the M.E. in his presence in a sort of social slight. That might paint a different picture : so far gone the cops don't mind badmouthing him within his hearing.
If we start with two cops having a bitch session over a dead body that tells the reader something. If we start with cops on scene and an M.E. puking, walking over and having the cops bitch about his professionalism within his hearing, that's something else.
It isn't that one inherently works better. It's that one is the direction we chose to begin the scene and the other is follow-on action that we show but not as the opening. One, to me, proceeds linearly as the reader tries to answer WTF in the first paragraphs. In follows the
in media res maxim but requires a "information after we've met you" style.
If the information about a character influences or perspective of his actions, it is nice to have that context before he acts. It isn't essential.
What matters is that the manner in which we cast our scene is in harmony with the pace, manner, and perspective we're trying to convey to the reader.
Starting the scene with a cup of coffee at Starbucks that isn't going to stay down once Williams reaches the scene: probably not sufficiently immersive for orientation. We drop that part. We move on.
I need to write some scenes. So do you. Where we start the scene? As long as it works, it works.