Every scene must have conflict.
Simple, I know. But not really. First let's break that down into its fundamental parts.
Every = no exclusions. Every scene in your story, no matter how lengthy or short, has to have some kind of conflict.
Scene = anything between scene breaks or chapter breaks. Even if that scene/chapter is only half a page long.
Must have = (again) no exclusions. Repetition for emphasis.
Conflict = internal or external hindrance to a goal
Based on the definition of conflict, then, you can reasonably assume that every scene must also have a goal. Without a goal, conflict is not possible.
Conflict is what keeps the tension high and keeps the reader engaged, so if conflict is not possible without a scene goal (or a story goal overall), then we can rightly say that you must start each scene with a goal in mind.
I admit, when I first started writing "professionally" I didn't understand what it meant to have a goal for each scene. (I also didn't fully understand the idea of conflict. Not surprisingly, the two go hand in hand.) When I read about giving your scenes a specific starting goal, I thought that meant you had to spell out the goal for the reader.
But doing that doesn't give your reader the intellectual credit they deserve, and starting every new scene with something akin to "I need to get to the post office before they close or this very important package will be late, creating a maelstrom of devastating consequences" doesn't make for very good reading, either.
Scene goals should be fluid, seamless, to the story already in progress. In fact, your reader shouldn't even notice them as specific, laid out goals half the time. What they will notice, if the scene goal is presented well, is the conflict. The reader will have a sense of "this needs to be done, but this other thing is preventing it, oh crap." And that's what you want.
The audience is made aware of the goal because of the obvious push of whatever is trying to stop it. Not because you, the author, have spelled out the goal for them on the page. When the reader feels the conflict more than the goal, they will root for the success of that goal without even really thinking about it. It's a survival instinct. We want the good guy to win. We want the problem to be solved. We want the conflict to be overcome.
That isn't to say that goals should be invisible. Some of them, such as the goal of the main plot, should be very blatant. But that is an overarching goal that covers the length of a story. When you narrow things down to the scene level, it becomes more subtle.
And that's why it's more difficult.
I've seen the following example used on writing blogs to the point of wanting to shoot my own eyes out. Even veteran authors and editors have used it. Why? Because it's basic, and teaching at the basic level usually gets results. But in my opinion, they've created more confusion, or worse, an illusion of understanding. Beginners, especially, now think that they have to write their scenes with a basic format like this:
Bob walks into his boss' office with the intent of asking for a raise.
His boss tells him he can have the raise after he proves his worth on the newest company project.
Bob leaves the office with a new goal (ensuring the success of the project) because doing so will help him reach his original goal (getting a raise).
It's a good foundation on which to build conflict. But it's not in story form, so when referring to an example like this we miss a LOT of what is essential in making it work-- the delivery.
A good delivery involves multiple layers of conflict and shifting scene goals.
I recently read the most perfect example of effectively presenting scene goals and conflicts in the opening chapters of EVERYTHING YOU NEED TO SURVIVE THE APOCALYPSE by Lucas Klauss. If you'd like to follow along, click here to view the sample chapters.
In chapter one, the conflict is immediate. The first three lines are a repetition of the word "ow." Pain is an effective inner and outer conflict because the goal is so simple-- get rid of the pain. Human nature makes us want the pain to be gone, no matter where it came from or who is feeling it. By the end of page one we understand where the pain is being felt and why. This helps us figure out how the viewpoint character can possibly overcome the conflict.
And there you have it. A scene goal and immediate conflict right in the reader's face by the end of the first page.
As the chapter rolls on, however, we're introduced to yet another conflict-- Ferret, the track coach. He isn't very well liked, especially if it appears that you are just standing around, even if you're not moving because you're injured.
So the scene goal has just shifted, made clear by the new conflict. Now the viewpoint character needs to somehow avoid the wrath of his unreasonable coach. This leaks into the next chapter by way of a cliffhanger ending of the first chapter. Someone does catch up to him, but it isn't who he was expecting. Is this person better or worse? We aren't sure, so we keep reading.
Chapter two begins with a new scene goal, (again) made clear by conflict. Our brave pain-fighting hero from chapter one has now become a blubbering idiot in the presence of a girl. He wants to appear cool and confident, but his track record isn't so great. He somehow manages to get the girl to laugh, but internally he's dying of awkwardness and wants to get away.
And just as that conflict is now seemingly evaded, the next is riding hot on its heels. The coach is approaching, and Phillip has clearly been not running like he's supposed to be for a good stretch of time. The scene goal shifts, made clear by the conflict. He now has to face his unreasonable coach with this girl still hovering close by, making him feel all self-conscious. This multi-layered conflict, both internal and external, makes chapter two an even better read than chapter one.
It continues in the same manner from there, chapter after chapter of shifting scene goals and facing new conflict. That's how you keep readers reading. Without conflict, there is no sense of urgency, no tension. Without a scene goal, you have no conflict. But it all has to feel seamless, natural, as you're reading the story.
So when you see the advice "every scene must have conflict", it doesn't necessarily mean that every scene must be a life or death situation, or even feel like a life or death situation. Conflict comes in many forms and different levels of intensity. What you use and how you use it will depend on the individual needs of your story.
The best thing you can do to see what is appropriate for you is to read novels that are similar in genre, style, and scope to yours. Analyze how the author balances between scene goals and new conflicts. Apply the techniques you think work best.