Updated June 12th, 2019.
If you have a big mess of files on your Desktop you know you ought to put them into folders… but it’s hard and no fun so you don’t do it. Here’s how you can make it a little bit easier and a little bit fun.
First, select some icons on the desktop that you’d like to put into a folder. Don’t bother making the folder first– we’ll take care of that shortly.
Then, go to File/New Folder with Selection. When you choose that, the icons you selected previously all jump into this new folder. The folder’s name is highlighted so all you have to do is type the name you want, and press Return. Pretty neat.
Note: this technique is not restricted to the Desktop. You can select items in any Finder window and choose New Folder with Selection and those items will jump into an automatically-made folder.
Note 2: in Mojave, you can use “Stacks” to clean things up, putting your files into little piles.
I like to “Group Stacks By” kind. You can do it any way you want. Click a Stack to expand it, find your file, and then click again to re-stack things.