Things I wish I knew before starting writing:

Write down a list of characters you want to be important in your story.

Keep track of when they were last important, give them lines if it's been more than 10000 words and they haven't said anything. (Unless there's a reason for the absence)

If you haven't written anything for a week or more, read the previous chapter and whatever you've written for the current chapter and familiarize yourself with the characters.

Write down a list of personality traits for each character, make it as detailed as possible so that you don't make your own characters switch personalities every other chapter.

"Independent" is NOT a good personality trait to list when trying to keep a character's personality in mind.

If you can't find an image that your story, just look up a picture of one of your main protagonists.

When you sit down, always prepare to write at LEAST 1000 words. Don't get up until you finish (unless you're about to be late for something important like say, working.)

Get a beta next time, you freaking idiot. A co-author, if you can.

Don't start a multi-chapter story while writing a multi-chapter story unless you're SURE that you can handle juggling the two.

Set reasonable deadlines, (2 chapters in a month, x arc by June, etc.) And write them down somewhere.

You don't even have to look at the place where you wrote it down ever again! Just writing it down helps! DON'T use wikia. It's a piece of crap that lags your computer.

If you have to use it often for the same few pages, copy the contents onto a google doc.

Don't keep secrets from your readers longer than you have to. A good mystery is nice, but dangling it in front of them like a juicy steak every other paragraph is probably going to piss them off.

If you suck at a certain type of scene, have someone else look at it. This is probably obvious, but I didn't do it, so I'm writing it down.

Look at other fanfictions for your pairing. If it doesn't exist (like Robin x Eirika), then look at stuff similar. (E.G: Eirika x Mark)

If your reviewers have a good idea, keep it in mind.

When you get your first reviewers, make sure to respond to at least a few of them if you want more reviews.

That's it for now. I'll probably write more later as I do more stupids. :P

EDIT: Just realized today that for some reason my entire list was underlined and in one ugly block of text. Should hopefully be fixed now.

UPDATE (06/14/2019):

First of all, I am hopefully back in the fanfiction saddle after a long hiatus. However, this comes with good and bad news.

Good news: I will be continuing Impact of a Hero. I will stick with this one until it's complete, which shouldn't take too long hopefully. I kinda like some ideas I have in mind for this story, and even though it isn't my usual cup of tea, I like what I've got going there.

Bad news: I am discontinuing A Chance to Matter. Honestly, this has been a long time coming, but I just haven't been able to bring myself to officially do it. I especially don't want to update that story just to disappoint everyone who reads it that all I'm doing is abandoning it.

So why am I stopping it? Well, a multitude of reasons, really.

First: I'm not a particularly interesting character. When I thought about the future of my story, I clearly was just becoming more and more of an OC.

Second: The way that the plot was progressing, the romance that I wanted to build was incredibly forced and had absolutely no time to develop. I love Ruby as a character, but because of the limited time frame that canon gave me, and my limited experience as an author, I just couldn't come up with anything to do there.

Third: I have lost almost all interest in the RWBY franchise. I haven't even watched season 6. I have absolutely no idea what happens in it, and I honestly don't care. I feel like Rooster Teeth should have kept everything at Beacon, and continued the settings that we were used to in seasons 1-3. I could go on a rant about this for ages, but I won't. Anyways, because of that lack of interest, I felt that what I had in mind just kinda wasn't good enough.

So with all that in mind, I'll be taking down A Chance to Matter on the first of July. Sorry to do this to people who liked that story.