During live performances, most bands play their best songs. Any tunes they just don’t play as well don’t make the set list—they get left out.
When a chef opens a restaurant, she doesn’t serve a sampling of everything she’s ever cooked. She puts her best dishes on the menu and lets those speak for her. She knows what to leave out.
A lawyer doesn’t give a closing argument with five convincing points and two not-so-convincing ones. He uses that time to drive home his five best points. Anything that’s not as effective, he leaves out.
When a good writer finishes a book, she doesn’t include every chapter she worked on in the rough drafts. Those that didn’t add anything or that just didn’t work, she leaves them out (and if she doesn’t, her editor probably will).
When you do your college applications, don’t just focus on how to present what you’re including. Think hard about what you’re leaving out. The one activity that you never did again after freshman year, that paragraph in your essay that makes it go over the word limit but doesn’t really add anything, that description in the optional “Additional Information” section that’s really just repeating something you’ve already listed elsewhere, you don’t need them. They’re not improving your application. And they’re just making it harder for the reader to focus on what was really important to you.
Every time you leave something out, everything that's left in will get more attention.