Writers love giving advice to other writers. For every one of us that achieves a degree of success--success being something measured on a spectrum, much like mental illness--there is someone who has not yet reached the same degree of success asking for advice. And we will give that advice, because there's nothing that says, "I am the special snowflake I think I am" quite like explaining how we did it.
This means there's an awful lot of advice out there, which is great, except when it's not. Here is some advice about all of that advice. Feel free to ignore it.
Outline before writing, or don't
For some reason, when writers don't outline it's called "pantsing", as in, "writing by the seat of your pants". You may wish to outline solely because "pantsing" is a terrible made-up word taken from a clichéd phrase that nobody actually understands.
I personally can't outline, because I have this problem where once I've written something down it becomes real, and then I can't change it even when the story calls for it to no longer be true. Likewise I can only seem to reach the end of a story if I'm not entirely positive how the ending is going to play out. I'm often as surprised as anyone. (Sometimes, I'm also awed and horrified. The end of Sapphire Blue was about ten times crazier than I thought it was going to be.)
I know plenty of writers who outline, and write character sketches, and know all sorts of things about their plot and characters that never make it into the book. God bless all of them. I can't do it.
If you're stuck, work on a different scene in the book, or don't ever do that ever
I know one writer who jumps from scene to scene so often she has to arrange what she's finished on the floor like a collage before figuring out how to connect it all into a cohesive whole. This is because she keeps jumping to the scenes she wants to write next, even when those scenes aren't necessarily the ones that come right after what she'd already done.
The advantage to this approach is that you're always writing, and there's certainly some good things to be said about that; continuing to write is almost always better than not writing for a while. But much like outlining isn't something I can really do, I also have to write from beginning to end. Jumping into the middle means making certain assumptions about the plot that will lead to that scene that may not end up being true, and I hate that. So I don't do it. Instead I have days when I don't write at all up until I've figured out what is supposed to come next.
Write every day no matter what, or not
I don't want to write every day, because I have other things to do, and I don't particularly want to feel guilty about it. I get that this is something you must practice in order to improve at, but it's also true that forcing yourself to do something every day can make you hate what you're doing. I may be alone here, but I've found I'm not a very good writer when I hate that I'm writing.
Just keep writing until you reach the end, and worry about the stuff you need to fix in the second draft, or fix it as you go if you want to
This is in the same spirit as the write every day advice and the write the book out of order advice, and probably has a little to do with the idea of an outline. And the advice has merit, because finishing the novel means you have reached that point where you have an entire end-to-end story you can hammer at in edits until it looks like you thought it was supposed to when it was just a beautiful thing in your head.
But I like editing my own stuff. I like it so much I will sometimes do it before I even know how the rest of the novel is going to go. Editing is my solution to writer's block, and to working on writing every day without actually writing every day. And it means by the end of my first draft I've usually also reached the end of my second draft. I also hate writing something that's wrong when I know it's wrong, even if writing it means I can eventually get to something that isn't wrong.
Listen to advice, and don't listen to any advice
Here's the secret: writing a novel is really hard. That's why writers will fall over themselves to tell you how they did it, because frankly nobody else quite understands the degree of difficulty we're talking about. At the same time, the difficulty is why we sometimes seek out the advice of other writers, especially if we are having trouble finding a way to the ending of our own novel.
All that advice really amounts to is, "this is what worked for me". That's great, but there's no reason to think it will work for anyone else, and more importantly there's no reason to think that there's anything wrong with what you're already doing.
If you're struggling, it isn't because you're doing this wrong, because there isn't a wrong way to do it. If you're struggling, it might be because writing a novel is difficult.
If it wasn't, everyone would do it.