Ah... so we've come to discuss the tenses. First I will go through each of them and discuss the pros and, of course, the cons. Hopefully this will help you decide which one to use when writing.
Part One: Past Tense
1. What is Past Tense?
Past tense is usually the type of thing you would be seeing in your books, unless you usually read YA fiction because that particular category tends to have more present tense. It shows something that happened. Almost like someone is relating a story from their past, hence the name. There is two ways to look at this. a) Someone is relating things that happened to them only a few seconds before or b) they are talking about something that happened years in the past. If you are telling a story in past tense, decide which one is true. If it is the latter, your character might have some insight on what is to come in the future. If it is the former, don't be dropping hints about the future unless they have some future-reading power or something.
2. The Pros
One of the pros of past tense is that it is possible that your character might have some insight on what is to come and can drop little hints everywhere (I already said that). This tense also tends to appeal to more readers since it is what we are used to reading.
Also, you can write in third person naturally, if that's what you're into.
3. The Cons
Please know that if you are writing in the past tense, it may not be your best option if you are planning on killing your main character. It complicates things, however subtle it may be to your readers. There's always going to be that one critic that rips your story to shreds and reads into every single word you typed up. Since you are technically writing in the past, it means that the events you speak of already happened. If you write in first person, in the past, who is relating your character's death as it happens? Certainly not the person who just died because they wouldn't be alive to tell everyone about it.
4. When would you use Past Tense?
I'd say that the most effective time that you would use past tense would be if your character is old and is telling a story to their grand-children or something along those lines. Or if you just can't write in present tense. Really, I'd say you can do it whenever the hell you want! Assuming you aren't writing in first person and want to kill your character.
Part Two: Present Tense
1. What is Present Tense?
Present tense is the tense where everything is happening in time, with the character in the book. The character has no idea what comes next. Everything is new and unexpected to the character (well, sort of). Instead of the narrator or character (depending on the point of view) giving little tips at what might happen next, you have to use foreshadowing to give this same effect.
2. Pros
First of all, you can kill your character! *inserts happy face* If that's what you want, of course, then this is good news. Another pro is that your characters will be doing everything with your character. It's like you, as an author, pulled them along for the ride, instead of just letting them observe what happened. If you really want your readers to feel and understand what your character is going through, this might be a good bet.
3. Cons
A lot of people find this difficult and sometimes awkward to read and to write. Sure, your readers will get used to it but this tense can be hard to master if you actually want to write it. Plus, third person is very, very awkward to write in in present tense unless you are a master literary genius. I do not suggest for you to even attempt it unless you've published ten novels, if even then.
4. When would you use Present Tense?
Like I previously mentioned, if you really want your readers to be in the moment and experience the story at the same time as your character does, this is a great way to go. If you are confident in writing in this way, by all means, try it! And, of course, if you want to kill your character, this is always a safe bet.
Part Three: Future Tense
1. What is Future Tense?
Sure enough, you guessed it! It is where you say what is going to happen. What you are going to do. It hasn't happened yet, but it will. Future tense is barely seen in any form of literature, but you may happen to stumble across it from time to time.
2. Pros
Future tense is rarely seen in novels. In fact I don't think it is used at all. The only pro that I can honestly think of is that it represents a decision that your character has decided to make. Instead of just rolling with the crowd, they made a choice. I will stand up to the bully. I am going to try my best to get into Yale. Future tense can show strength. But you should never make it consistent in your novel. Just used here and there. For past and present, you have to make a choice: one or the other. But future tense is used like a seasoning, sprinkled here and there.
3. Cons
You can't actually use future tense naturally, even if your character can read the future. It just sounds so weird. Yes, that is a con. You simply cannot tell a complete story using it.
4. When would you use Future Tense?
Well, I can't think of any piece of poetry off the top of my mind that uses future tense, but poetry breaks a lot of literary rules. If you have this magnificent plan for a poem using future tense, don't let me stop you. However, never ever use it as your main tense in a novel or story. It will not work. Your story will burn in the depths of hell.
Sorry.
Some important things to remember about tenses is that you should not switch your tenses halfway through the story or, even worse, every few sentences. However, you can have your prologue and epilogue in present and the actual story in past. I've done this before. It works if your prologue, for example, is taking place in the present and the rest of your story is something that they are telling you. Or if your character moves in and out of the past, you can potentially switch it up. I do not recommend this unless you know precisely what you are doing.
Also, past and future tense can be used occasionally even if you are using present tense, if you are relating something that happened in the past (like a flashback) or something that you intend to do (a plan).
That's all I have to say about tenses. Feel free to ask me questions or point me out where I'm wrong. Thanks!