This is for those who are trying to upload a media file, but getting an error message that looks something like this:
Unable to create directory uploads… Is its parent directory writable by the server?
Because so many have been beleaguered by this problem, and many of the threads addressing it are three pages deep with lots of failed solutions, info on older versions of WP, and language that's confusing to a beginner, AND because I found a really easy solution that works, I'm posting this answer I found buried on page 3 of a 4-year-old thread.
(Your mileage may vary, depending on your host and the version of WP you’re using. The website I used this on is hosted at SiteGround, uses WordPress 3.6 and the U-Design theme.)
Go to Settings > Media. Or possibly Settings > Misc. on older versions of WP.
See that field in the middle of the page, titled “Store uploads in this folder”? You want to remove all of the text that’s in that box, and replace it with just this:
Then, click the “Save Changes” button. That’s it! You should be good to go.
I've posted more detail including screenshots at http://janasnyder.wordpress.com/easy-fix-for-media-upload-problem/.
Note: If this truly does work for everyone; WordPress, would you please add it to the Codex under Troubleshooting FAQs?