What, in your opinion, would be the best ways to approach writing a book?
I'd like to know what possible readers have to say, if you all don't mind.
- answers

As a writer myself, I can tell you that the best way to write a book is to write a book. And the process is different for different people.
Everyone usually begins by sitting down and writing out some ideas. Jot down outlines of scenes that stick in your mind. Write character descriptions and descriptions of setting and place.
You may discover that your imagination can carry you a long way, but most writers hit a block eventually. When you do that, write an outline of your plot. It can be very detailed or very simple, depending on what you need. Some writers start at the very beginning with an outline and others don't do it until they hit a wall, but in general an outline can carry you through spots where your inspiration leaves you.
Many writers find a community of like-minded people helpful in sticking to their goals, and this is where classes and forums can come in. You can join one online or in person, but it's lmportant to make sure it's a group of people who match you in the type of writing they're doing and their drive to succeed.
Classes in grammar and writing can help, but they're not necessary--and you don't need an MFA to be an author. You do need an MFA to be a writing professor, so look into that if teaching is a goal you wish to pursue.

I think that the answer that Ben provided for your last question is probably the best answer to this question as well. By taking those online courses you will begin to build a wide base of understanding for the process of writing, and will also begin to develop the concept for the book you would like to write.
Also, try working with an online writing forum. There are a number of writing groups that convene online, and workshop fellow writer's work.
Through both the online courses and writing workshops you should be set in the right direction for writing a book.
Best of Luck.
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