As mentioned before titles are important because they are the first impressions of your stories. So you better don't fail that part, think about going on a date in your worst clothes, not cool.

Definition of a good title: It fits the story and is catchy/original/funny

On AFF a good title might also be one of those generic titles if you want to catch attention of certain audience, make sure you tag your story properly.

So what do you want to go for:

a) original/ mysterious - More Than Amazing/ Purple Tomato

b) funny/fizzy - I'm his Candy Girl/ Chocolate Chip Cookies and Milk

c) descriptive - Living with the Worst Jerk/ We Got Married

d) weird - titles that make no sense or have major spelling mistakes (hopefully this is not what you are after)

I conducted a small research:

Titles which scored high in review shops (4-5/5):

Aish! That Jung Daehyun! - Be Careful when Karma Knocks you Down - Hush Little Baby

Passenger Seat - The Musical - ManThe Perfect Mis-Match - Novalis - The Dollhouse: Clandestine

My Fake Fiancé's Brother - Almost or Finally? - WOOING LEE DONGHAE

OH MY TUTOR! - My dearest Wife - Memory in the Rain - What is Life? - I'm Back Until I Die

In the middle (3/5):

Myungsoo my Butler Boyfriend - Let us end this - SWEET BITTERNESS - School Days

Boyfriend-Girlfriend, Deal? - Blood War of Love - Fated to Love You

All I Could Ever Wish For - Kingka and The Number 1

Scored low (1-2/5):

Almost  -  A Life for My Boyfriend  -  My Charming Key - HAPPY TOGETHER?! - Stay, My Love..

An Angel's Voice  - 7 Guys And 1 Girl In One Group - MY LIFE WITH THIS DEATH NOTE GUY

Miss Sunshine - Silent Moments - MY KOREAN BOYFRIEND - My Extraordinary Soulmate - Ultimate Fan Girl 

From recommended section:

Touch of Fear - Oppa's Not My Style - When Night And Day Become One - My Biggest Regret - The Challenge

10 Things I Hate about You - UNDERCOVER LOVE - Jackass Boyfriend - Loving a Straight Man -

In Love With a Mobster - Little Steps - Broken Beyond Repair

What I liked:

Perfectly Imbalanced - Royal Flush - Payphone Kiss - Hope is a Dream - Just Living - Neverland - Talking To The Moon 

Of Cigarettes and Tar  - Royal Rumble - Oh Brother! - Undercover Dad - Boy in Slow Motion

Candy Freak - Missing Puzzle Pieces - My Hopeless Prince - Love Dictionary: Limits --No Results Found--

In General:

The most common category was (3/5) that's sort of halfway, not good not bad.

Not many titles scored 5 nor 1, most of them were 2 or 4.

Which titles do you like?

What I learned from this research is: nothing. I can't tell why some titles scored so low despite being good and how come some titles socred so high despite being so bad? What I liked was purely on emotinal basis so no professionalism there but anyway, I gotta agree that the worst titles were kind of lame.

Some say titles don't matter but I dare to say they matter. If you go to library without knowing what to read and go to your favorite section, be it horror or romance, when you start looking for an interesting book you pay attention to titles. What else? 

Naming your story might be difficult.  You might want to name it in a descriptive way especially if it's fanfiction because then it will be easier for readers to navigate and the lovers of certain genre will most likely click on your story if it’s about something they like. It all depends on the mood of the reader, what they feel like to read.

That Jerk Neighbor/Classmate/Kris

When you Met Sehun

His Slave

Maid in his House

He Got Me Pregnant

My Stormy Love with a Gangster

These titles are not original but they are good on AFF, very reader friendly. Sadly, by no means are they good if you want to stand out because they are very generic and overused, your story will drown into million other similar stories and be read by people who feel like reading that kind of story.

The most important thing is that your title fits your story. For example in my story ‘Effervescent Ambience’ the title bears a special meaning to the two main characters and these two words are repeatedly used in the story. In another story I wrote ‘Just a Big Fat Lie’ the title fits the story in a sense that everything turns out to be a lie, everything, even the main character so I think this title fits perfectly. ‘On a Perfect Autumn Day’ the title fits because it’s autumn and two very important things happen on that perfect autumn day, I was thinking about changing this title to “On the Tracks” because that sounds better. Anyway, the most important thing is that all of my titles bear some kind of meaning and I can explain why I decided to use them.

Sure if your story is about kpop band life then why not name it ‘After Auditions’ but if you want to come up with something more special then you will have to think hard. Usually titles don’t come easy so don’t start thinking about the title first, just start writing and think about it later. I always try to postpone the birth of a title as far as possible. The ideal situation is when I only start thinking about the title after finishing my story, works well with one shots.

A few tips:

a) Think about the themes of your story, what genre is it? Sad, funny or mysterious?

- If you write comedy or romcom then a pun in the title is always a catchy choice or a funny title in general: Elephant who fit in my Pocket, Vain Romance, Beautifully Disgusting, Love? I Ate it

- If it’s a melodrama or angst story then think about something sad or meaningful: Frozen Petals in Summer, Black Snow, Tainted Photographs, Melancholic Hearts, Dead Swans

- If it's action you can go for something explosive and speedy: Crashing into Misfortune, Running After Troubles, Exploding Emotions, Burning Lust

b) Think about some keywords used in your story, does your character often repeat something? Perhaps an interesting quote? A set of words?

For example: in one of my stories the main character often says something like this: “Getting soft is the first stage of rotting”, this is how he refers to love, so ‘Rotten Love’ or ‘First stage of Rotting’ these two fit the theme of the story as well as ‘Behind Broken Eyes’ and ‘Innocent Sin’.

c) Write down your all-time favorite words or look up some new words on dictionary, then put them randomly together (but so your title makes sense).

d) Use internet: search books with similar genres on google, amazon or yahoo. Don’t copy other people’s titles, use them as guidelines, gather a title by adding the words from existing titles together.

e) Challenging repetitive titles is always fun too:

He Got me Pregnant -- > Alcohol, Mistakes and Disaster, Thanks for the Gift, Our Beautiful Mistake, From Hangover to Pregnant,

Falling for You --> Falling on You, Falling at You, Falling Behind You, Right at You, It’s not Love I’m just Hungry, Woman from Mars, Man from the Moon

Living with 6 idiots --> Sharing is Caring, They are Everywhere, Stupidity Overdrive, Idiocy Meter + 100, Complicated Circumstances,

I’m Maid for Exo/Kris/Myungsoo: Fire in His Kitchen, Where is my Thank You? Dusting off His Heart, I Found His Feelings Under His Bed, Across from your Room

I think you catch the flow.

And good luck with your titles!

Ps. Here is a good site about titles, do check it out.