For any new writer, novel writing that is, my advice is to know what you're getting into, as writing the novel can be the easiest part to the whole process. It's after you write 'The End' that the real work starts.
Firstly, make sure you have the time to write. It's very important. Teach your family to respect your writing time.
I have always wanted to write, but I didn't begin to write my first novel until after I had my third child and I was home full time. With one child at school, a toddler and a new born, I decided to finally put down on paper the scenes that had been playing in my head for years. I started my novel on a type writer, but then a few months later my husband bought me a computer. Writing my first novel was an amazing feeling. I could only spare a few hours each day as the kids were napping but it gave me such joy that I knew this was what I wanted to do forever.
Read contemporary books to get the feel of the style editors are looking for.
Don't let your mother or sister, etc read the book, because they will say it's great, just so your feelings aren't hurt.
Find a good honest, trustworthy critique group and listen to their comments - good or bad. Perhaps not everything they say will be right, but they should give you a balance to help with revisions.
Edit your work well. There are a lot of online writing courses and articles to help you perfect your work.
Be prepared to spend a long time sending out your manuscript to agents and editors. While the ms is out being reviewed, start writing another book.
The biggest obstacle when it comes to pitching your work to a publisher or agent is ignorance. Read up on the industry, join online writers groups and ask questions.
In the beginning, my biggest obstacle was ignorance. I simply didn't know enough of the publishing industry to query the right agents and publishers. I had to study the market, the publishers, the agents and learn who was suitable for my writing. This took awhile and I made some terrible mistakes, but I call it my apprenticeship. I think writers need to research the industry and target the correct agents and editors who represent the type of work they write and not send out queries to just anyone.
Once you have signed the publishing contract, you'll be expected to edit the work again, working with perhaps more than one editor from the company.
Often you won't have a say in the cover, and if you are allowed to provide ideas, you may have to accept the first cover made and not ask for changes.
Once the book is released, you'll have the promoting of it to contend with, but that's a whole other story.