Which is why I've decided to start my Quick Tips Series and they are geared for aspiring authors who wish to polish their work.
So first tip - the use of tenses. Always remember that you need to use the SAME tense throughout your book.
THE RIGHT WAY
"Hi," the girl SAID.
The boy IGNORED her.
She REPEATED, "Hi."
The boy still DID NOT look at her.
Above, we've used PAST tense throughout the scene.
THE WRONG WAY
"Hi," the girl says.
The boy ignored her.
She repeats, "Hi."
The boy still doesn't look at her.
Now, with the above example, I've mixed past and present tenses. That is a huge NO-NO. Like, one look at your sample pages and agents you're querying will immediately hit 'delete'.
Now, if you're thinking - which tense should I use?
I think it's safe to say that PAST tense is the conventional choice. However, it's become increasingly common for present tense to be used in YA/NA/Erotic romances simply because it makes the story feel more intimate, like you're really a part of what's happening.
Ultimately, this is a subjective choice, one that has to do more with your writing style and preference.
Just be aware that there are a number of agents and publishers who distinctly dislike the use of present tense. We can't blame them - to each his/her own. :)
P.S. Please do not consider this post as an indication that I'm a great writer. I am not.