The classic beginning for a certain kind of story is, “Once upon a time . . . .”
That tells you something immediately. It tells you that the story is set in the past. The events are over, the girl and the boy either did or didn't get each other, good either triumphed or got trampled, and some characters survived (if it's the kind of story where that's in doubt), while others didn't.
Past tense is the classic way to tell a story, whether it's set in the past or in the present. (Or, even, in the case of speculative fiction, in the future.) The teller of the story is separate in time from the events of the story. The great epics of Greek and Roman times, the enormous novels of the eighteenth century, the fairy tales of the Brothers Grimm, the stories Scheherezade tells in the Thousand and One Nights, the vast majority of novels written today – all of them are told in the past tense.
Essentially, the writer sits you down, figuratively speaking, and says, “This is what happened.”
There's something magic in this. It invites you into a world that's separate from yours, in a time that's separate from yours. It says, Look – here's an opportunity to get out of your own life and into a place where anything can happen. Watch kids sometime when someone begins to tell a story with “Once upon a time.” Their imaginations are engaged instantly. They enter that story as though there were an open doorway leading into it. For all intents and purposes, they're no longer in the room.
If it seems most natural to you to set your novel in the past tense, more power to you. You're in great company
But I want to put in a word for the present tense.
I've written six novels in the past tense, all in first person. One thing always troubled me a little about the approach. It was obvious from the beginning that my narrator survived the story, or he wouldn't be around to tell it. I also felt that the past tense distanced readers just a little, an imaginary millimeter, from the action or suspense sequences, which are relatively frequent in my books.
When I sat down to write the Bangkok series, I did my usual warm-up (we'll talk about warm-up later), and a lot of it was first-person material from the perspective of four or five of the main characters in the series. About 30 or 35 pages in, I realized I was writing all that material in the present tense and that I liked it.
It had an immediacy I enjoyed. It was less like writing and more (do I dare to say this?) like a movie or a play. Plays and movies exist in a permanent present tense, a period of time that begins the moment the curtain lifts or the image hits the screen. The viewers enter this period of time with the characters, and live through it right beside them. (This is an interesting illusion because it holds even when we see a film for the third or fourth time.)
I write in part for fun, and I thought it would be fun to try to preserve this sense that things were happening at the moment the reader reads about them. And it was fun, although old habits die hard and I had to go back literally hundreds of times and correct verbs I'd accidentally written in the past tense. And, as the pages began to pile up, it seemed to me that it was working. It seemed especially effective in the action scenes, which began to feel less like hearing a description of a fight and more like actually being in one. So I stuck with it, and for better or worse, I'm now committed to writing a series that's set in the present tense.
In the past few years, more and more writers have chosen to tell their stories in the present tense. It's become something of a trend, although some editors (and, for some reason, agents) don't like it. Hell, there are times I don't like it, either. But for my present purposes, I think it engages the readers more closely in the story and the lives of the characters (which are, or course, the same thing). I'm not sure it would be effective for all stories, and I don't think the past tense is in any danger of extinction, but you might just consider the alternative.
If you have any interest in it at all, give it a few pages and see whether it works.