1) OCs. please don't use them as main characters.  WTF? what we want are our OTPs, not some random self-insert!  OCs are okay as plot devices or the villain (secondary love interest that is the bump in the road for our OTP)  capisce?

2) images interrupting the plot!  Use your ****ing words.  Use asterisks to signal any images that you might use that are posted at the end.

3) POV changes.  You don't need to put "SO & SO POV"  you can indicate a new paragraph.

Youngjae turned and looked at him, grinning.

His smile was LED.  I couldn't help the way my heart started beating faster.  I swear my cheeks were tomato red, from the way they were most likely radiating heat.

"Gukkie?"  He held out his hand for me.  I took it.  I think I could fry an egg on my face.  That's how bad it was.  "So cute."

Youngjae laughed, as the older man ducked his head to hide his burning face.

"I-I'm not a girl!"

4) italics for "thoughts" or in brackets!  Okay, if you really want to use thoughts and stuff separate it from any other points of view either by

doing this:

He looked at the boy like he was .  He scoffed, wrinkling his nose in disgust.

I hated the guy the minute I saw him.

OR

He looked at the boy like he was .  He scoffed, wrinkling his nose in disgust.

I hated the guy the minute I saw him.

The second option isn't my favourite, but it works without being as distracting.  The first is the least distracting.

5) use of unnecessary words.  What the hell are you talking about?  What's the context? 

He is beyond words. OR He is perfect.  NOT He is perfect beyond words.

6) grammar and syntax, esp. verb tenses and singularity/plurality. This does not bother me as much, as they could be the product of typos.  Everyone makes them.  So do I.