It can be hard to truly focus on the important parts of your design, or goal, or company, when thousands of things seem important every day. To keep this focus, you need to identify your Key Action, and work backwards from there.
Before you begin designing anything or making product choices, you need to know what your goals are for the design or product.
i.e. — What do users want to do, and what do we want them to do?
Ideally, users and the business will meet in the middle so the business benefits when the user achieves their goal.
But when, exactly, does that happen? What is the exact moment — that one click or tap — that achieves the user’s goal?
For an e-commerce site, it is the “complete purchase” button, because there is no purchase until you click that button.
For Facebook, it is the “Post” button, because if nobody ever posts anything, the whole social network grinds to a halt.
For a porn site, it’s choosing a video to watch, because if nobody chooses a video… yeah.
The point is, you need to find the specific moment when the user goes from ineffective to effective.
If you could only have one button on your entire site, this would be the one.
That is your Key Action.
Once you find your Key Action, start to work backwards.
If you go one step backwards from the Key Action what must the user do or need right before doing the Key Action?
If it’s a shopping site, maybe they entered their credit card number.
On Facebook, they needed to add content to their post.
On the porn site, they needed to know if the video is about gay midget bondage or albino foot-fetish role-play.
Once you know the step before the Key Action, you know how the user will get to the Key Action, and the most important thing they need to take that step.
For each step, decide what is necessary.
Entering a credit card number might sound simple, but what does it require? The number. The expiry date. The CVC number. Anything else?
A Facebook post needs some text, at least. The ability to add a link or a photo also seems pretty important, so maybe we can say those are necessary too.
Choosing a porn video (or any video) means a thumbnail image and a title, and maybe knowing how popular the video is, or how long it is (not that you’ll get to the end of it, but ambition is a good thing).
When you know what is necessary, design the best version of those things, and nothing else.
And… many steps will have a Key Action of their own. Submit the credit card info or choose the photo.
As you work backwards through all the steps that eventually lead to that one, final Key Action, you will understand what is necessary to perform the main purpose of your app, site, page, or whatever.
And only that purpose.
Using this method creates a “straight line” of functions. It is very focused design work.
Some steps might involved browsing or searching or writing which are not “one thing”, and may include several features to make them useful.
If you need those features, include them. If those features are not make-or-break features to get to the Key Action, don’t include them (for now).
Eventually you will reach the beginning, and there will be no “previous step”.
Then you’re ready to start designing, because you have identified every fundamental ingredient necessary for the user to get from A to Key Action.
Good luck. :)