How to Choose a Publisher
You Have a Manuscript
Be Sure You Edit
You want your manuscript to be as close to perfect as you can get it. Get it edited. Find a retired English teacher to read it over for grammatical errors. Have someone with no vested interest in it read it for content, make sure it is consistent.
Finally go to your 'find' button on your word program and click it. Type in the word "that" Eliminate it or find better word. Unless it is a specific thing: that folder, that pen, etc. DO NOT use it. It screams beginner. You don't want to be seen as a beginner. Check your paragraphs and make sure they do NOT start with the same word. Same thing for your chapters. Each should begin with a different word.
Now you are ready to submit.
Know Your Resources
Preparing to Send
Use the Writer's Market to find agents, publishers, magazine outlets for your writing. It is probably the number one source for where to find agents.
Read all the guidelines. Submit only what is asked for. Do not embelish. It's okay to tell them this is your first novel. Have a great two sentence hook, something to make them want to read more.
Follow directions for delivery. If they only accept email, it's what you send. If they want snail mail, send snail mail.
Make your bio brief, but highlight your accomplishments. Especially as they have to do with your writing.
You Want to Self-Publish
This is where it gets tricky. You don't want to wait years and get 50+ rejections, you want your book out there now.
To choose a publisher first check preditors and editors. www.pred-ed.com. Look at what is says about the different publishers. If it says vanity press, know they take anything and will charge you an arm and a leg. They will give you 20-40% of the royalties. Wait why so little? You paid them up front.
Small presses who have a good reputation will be a good start. A true publisher does NOT charge you money. They do offer a contract. You can expect 60-65% royalties. Find out all you can about them. See some of the books they've designed. Talk with them and find out if they are a fit. Do a second check on writerbeware.com. If they pass both preditors and editors as well as writer beware, you are probably pretty safe.
The third option is to hire a design team to do you set up, interior and exterior design. This will cost you money. About $500-$600 per book. The good news is you have your own book imprint, meaning you can get into bookstores. You can upload to both Createspace.com and KDP for ebooks. Even better you get a monthly statement of sales from both. Now here's the best part, you get 100% of the royalties. You can have your books in book stores like Barnes and Noble, Books-a-Million and countless other stores.
Whatever You Decide
Do thorough research. Talk to writers who are published. How did they do it? What were the hardships? Yes, marketing costs money. Yes, YOU are responsible for marketing even if you make it to the Big Six.
Learn about marketing. Create a marketing plan. Map out book signings. Get to know the local librarian, newspaper reporter, radio personality. You have to get the word out. No one will do it for you. Get your family and friends on board. Have a book launch party, pick a theme which will compliment your book.
If you go with the traditional publisher or the small press, get a contract in writing. Read it thoroughly. Have someone who knows literary law read it. Get everything in writing.
Best of luck to you.