it has to draw you in, make it so you feel like you're right there watching the whole thing. It has to strike you over and over and over until you can take no more and need a cold shower once it's over
you just need to practice writing lemons more i think. But to write a good lemon it just has to be able to pull the reader in, make them want to read more. For me a lemon cant just be a simple 'wham-bam-thank-you-ma'am' it has to have an erotic appeal and that is how i try to write my lemons too. To be sure i've messed up a few lemons, but those i tend to edit and if i really cant salvage them i just dont post them.
to me lemons are more than just sex in text-form, its an art form too. When a lemon has been incredibly well you don't just appreciate it for its fappability, you also appreciate the way in which it has been written in.
The one thing that turns me off a lemon the most is crude, simplistic forms of description/writing style.
Note: writing one-shot lemon stories with just sex in it is a good way to practice the way you write a good sex scene. Don't have to publish them, but if you feel that they are good enough to be published as one shot PWPs for its erotic/artistic value then do so.
Remember, any story that is a lemon, the plot will always be sex focused. Remember this aspect.
So that means that any bit of story you write, is always going to be about leading to the sex. So if you're going to have story outside of PWP level, you need to remember that it should be at least leading to the smut.
The story should not be "Ladedah, hey let's suddenly have sex in the middle of this!"
As for a sex scene. Well, what a lot of people forget is that sex is not just the physical actions. You can go "I slid my cock into her and continued to pound her." But that's not doing anything.
Emotions people. Sex is very much about emotions. What type of emotions are you inspiring, what do your characters feel, why do they feel this way.
If you're a virgin, well chances are you're not going to be able to write a good lemon. It's kind of the write what you know thing.
And for the love of God, DO NOT GO OVERBOARD WITH THE NICKNAMES! I don't need to see dong, dilly, and so on. Same goes for talking about size. "OMG! He has a 9-inch dick. It doesn't hurt even though I'm a virgin! AHHH IT'S SO GOOD!"
to me, the balance of 'fapness', grammer & writing, story, plot, and other important factors make up the general lemon. like any story, online or not, they must be appeasing to the audience one is conveying their works to.