This should be considered as optional, but I will explain and show you why I like to remove my WordPress media settings which are preset when you first install WordPress. If you go to:
Settings >> Media >> Media Settings
…you will see the following media sizes and other settings:
Now I will show you what it does by uploading 17 photos to my Media Library…
With Media Settings
As you can see, WordPress will automatically generate thumbnails based on the settings (sizes) whether you want them or not. In fact, my media library went from 17 photos to a whopping 56! Why would you want to remove the settings? Because your hosting package has a certain amount of diskspace given to you, so if you upload a lot of images on a regular basis, that diskspace is going to get filled up fast and you will be billed by your hosting company for additional space requirements. Plus, if you keep regular backups of your site (as you SHOULD be doing), it means your backup files will continuously get bigger and bigger over time.
Without Media Settings
With the same 17 photos I uploaded, but removing each thumbnail size settings, this is what my media library now looks like:
Cropping and Organizing Settings
If you notice in the first screenshot above, the Cropping and Organizing under Uploading Files are checked. I would also recommend unchecking both. For cropping, I prefer to do my own cropping for more control over what parts of the image are to be cropped.
For the Uploading and organization of your photos, I really cannot stand how WP organizes photos and other media. If you have a lot of uploads over a span of a year and you realize you need to find one to edit, good luck! Very hard to find with the 10’s if not 100’s of sub folders it creates. I prefer to have them go directly into the uploads folder — all together.
Recommendation is to make each media size setting as 0 (zero) and uncheck both of the checkboxes. When you need an image for something, crop the image yourself, optimize it, size it, and then upload it.
If you would like to have one thumbnail size generated for a particular use and to maintain an easy way of having the same size for every photo you upload, you can change any of the settings to include the thumbnail size you want. So if you want a particular thumbnail size (that gets automatically cropped as well) for your blog featured images, you can decide on the size you want.