Your reader is always reading in the present. They might remember a past reading of your book fondly, but they're really remembering losing themselves in your story back when they cried in their present while identifying with your main character in your story's present, even if that was 1850.
The present tense connects the 'now' of your reader with the 'now' of your story proving that time travel does exist. But even in 1st Person stories where you're emphasizing the 'now' of the main character, most of the verbs are in the past tense. In my 1st Person YA mystery/thriller, "Wasted in Waldport", the first six paragraphs use 21 present tense verbs, but 28 past tense ones.
In 3ed Person stories the past tense rules, but, even there, hypothetical events are in the present tense. Ex. John planted (past) cherry trees, but would (hypothetical) go (present tense) to the nursery when he needed (past tense) more stock.
My first six paragraphs in "wasted in Waldport" establish the first scene mostly using the past tense: woke, was, was, (had set - past perfect), was, timed, let, was, was, spread, used, passed, have, was, stayed, was, dragged, added, trudged, showered, had known (past perfect), was, have gone (past perfect), turned off, kicked, started, was, roused.
Present tense ones anchor the 'now' of my story; is, chip, wear, get, comes, has, are, (wrangling - present participle), win, can (auxiliary verb) use (hypothetical action), smell, is, look, am, take, is, (would) do (hypothetical action), need, lives, end up (transitive), think, is.
You can make the connection to the 'now' with a skillful third-person point of view (POV), but it's not as easy as telling what's happening from a main character's first-person POV. Third Person POV tells your story in the past tense, but, even there, dialogue puts your characters in the present. Ex. John said (past tense) to Sarah, "Let's go (present tense) to the store."
In a future chapter, I'll spend more time on first-person main characters, but this chapter will assume that's the POV we're all writing from.
There are dozens of terms (hard to remember terms) for various varieties of the present tense verb forms. Later, I'll list those terms with one or two examples each to explain them. My examples will not successfully explain the terms, but you can match the verb form in your sentences to the example and name the tense or mood you've used. You'll only be right eighty percent of the time, but it's beginning.
Luckily, if you concentrate on the goals of the present tense, you won't need hardly any of those difficult terms.
Goal #1: Tell what your main character sees, hears, tastes, smells, touches, and feels emotionally. So, the five traditional senses and the internal emotions (relating to the five senses or completely unrelated to them). What about balance, hunger, thirst, and nausea? They're not senses or emotions. Right! But they're just as great and immediate.
Ex. Past: I lit a candle, and burnt myself with the match almost starting a fire when I dropped it. Susan must have thought I was an idiot. ('Must have' implies Susan hasn't told him yet what she thought, or, you'd have to add ' when that happened.' making your sentence an even bigger mess at explaining the past.)
Ex. Present: The match flares. As I watch the candle wick light, I yelp with pain. The match drops into the straw and I crush it with my boot. Sulfur and burnt hay are all I perceive as I suck my thumb. Susan must think I'm an idiot. She'll laugh at the blister I'll have tomorrow.
Does your finger hurt more with the present tense version? That's why it's the better choice, but you can get all of the past you want and the future too into the present tense by using the right verb forms at the right times.
