Delete the Harry Potter fan fic. Snape/McGonnegal was creepy anyway.
But it's just a 40 page comic in ASCII. How can that take up much memory?!
Apple is backing it up repeatedly into new copies because that's how the operating system masturbates.
Memory or disk space?
If I want to see what's using disk space this looks pretty and fun.
backup disks are so cheap now that you can surely just dump anything you're unsure of onto there.
"An" external drive where you back up photos? I would start by upping that to two or three.
Endorse 5. At least a backup for hardware issues that you can keep locally, and one for physical disasters that you keep elsewhere like at work and bring home to refresh a few times a year. Multi-TB drives are under $100.
For cleaning I think I used something called Main Menu Pro at one point. Haven't used it lately because I got a new computer and went with the largest storage option to avoid having to think about this problem.
Seconding NW's Daisy Disk rec. It has a nice graphic representation of disk usage in each subfolder, and lets you quickly home in on what's using a lot of space.
I have used Clean My Mac (macpaw.com) which is safe and good and adds to Daisy Disk's feature set specialised searches for the kinds of files that tend to take up room quietly in the background without doing you any good (e-mail attachments, application caches, etc) even though they're not obvious space hogs like audio & video files.
On the other hand, it's substantially more expensive and the developers push paid upgrades at you with annoying frequency.
If your file system hygiene is anything like mine (ie, disgraceful) then a duplicate-finder can also help with clearing up space. The Macpaw people make an overpriced one of those, too. (and of course there are others)
And this seems like the perfect place for me to offer a shamefully late thank-you to the commenter who offered a bunch of suggestions when I asked about apps for marking up pdf's a while ago.
I'm sorry I can't remember who it was (a regular, I'm sure) or what thread it was in, but it was a good and helpful list of suggestions and I wish I'd said so at the time but I didn't because distraction.
I use WinDirStat on Windows, which has a lovely graphical representation of what's taking up space where. Never came close to running out of space on my Macbook as I just used it for work, but when this topic comes up on other forums Daisy Disk is the one usually recommended.