When it comes to tense in fiction writing, there's one essential "rule" to remember: be consistent. If you decide you want to write in present tense, stay in the present. If you choose the past tense, stay in the past.
But how do you choose the verb tense to begin with? The best way is to understand the benefits and limitations of both, then decide which one serves your story best. Here's a little cheat sheet to help you choose.
- Immediacy - You feel like you're right there with the main character.
- Suspense - This is especially important if your story is one where the POV character is in peril. If the story is in present tense, the reader won't know until the end if the POV character survives.
- It Can Sound a Little Unnatural - Let's face it, present tense is relatively new in the world of fiction writing. Our ears are more used to hearing stories told in past tense (e.g. "Once upon a time there was a...") This is not to say that all present tense sounds weird, but for some writers, it may not come as naturally and could end up sounding hokey or gimmicky. The trick here is practice, practice, practice.
- Distance - The narrator has more distance from the events in the story it because they happened in the past. This gives the narrator some perspective about those events and allows the narrator to have some hindsight.
- Location in Time - Using the past tense, you also need to consider where the narrator is telling the story from. (This is especially important if you're using 1st person.) Is the narrator an old man looking back on his early life? Is she telling the story just after having lived it? Depending on where the narrator is NOW, it can effect how he or she tells the story.
- Less Suspense - If you're writing in 1st person or 3rd person limited and it's past tense, the implication is that the POV character has lived to tell the tale. In most stories, this is probably not a problem and won't kill much of your suspense, but if your novel is all about whether or not the POV character survives, then past tense could lessen the suspense.