1. Write a great book. This is very hard and will take you a long time. See (3.).
2. Never refer to yourself as: budding novelist, aspiring novelist, wannabe novelist, soon-to-be novelist, unpublished novelist, or any variation thereof. I AM A NOVELIST. You're either writing a novel, or you're not. What does "aspiring novelist" even mean? That you might write a novel one day? It says two things very clearly: I'm not serious about this (and in order to succeed, and be taken seriously, you need to be very serious yourself) and I'm not a very good writer (because 50% of your sentence is redundant, and gives--presumably--the wrong impression). Also: "unpublished" has many negative connotations. And it immediately provokes the question, why?
3. Take it seriously. See (5.).
4. Be professional, courteous and respectful at all times, to all people, both in person, on email, and on social media.
5. Learn as much about the industry you want to work in--publishing--as you can, because that's where published authors work. A published author is part of this industry. You see, your book is art, but when it's published, it's also a product, as well as art. If you're not keen on that idea, that's fine--scribble away to your heart's content, then put your manuscript under your bed where no one will be able to read it.
6. Meet as many people who work in (5.) as you can, either in person, on email, or on social media. Workshops, courses, talks, Twitter, websites, festivals, open days. This is not 1995. Literary agents are not mythical beings sat behind cherrywood desks and brass plaques in obscure parts of London. They are Real People. They are not "Gatekeepers". Their gates are flung wide open and they beckon you in, saying, please have written something wonderful so that I may take you on and sell it to a publisher on your behalf. It's down to you to write something wonderful. See (1.).
7. Never give up, and also know when to give up.
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Benjamin Johncock won the Authors' Club Best First Novel 2016 Award for 'The Last Pilot'.