One of the great things . . . and frustrating things . . . and great things about writing is that there's always more to learn. There's no such thing as a book being perfect, there's no such thing as knowing everything there is to know. The writer who understands that and accepts that will be a much happier writer because they will be able to say, "When I wrote my first book, I did my very best with what I knew then. Now, I'm doing the very best with what I know now."
When I'm working, I always have Merriam Webster up on a tab. I check spellings, but also hyphen placement. When you put a word into the site, scroll down and see all the uses. Here's an example from this last week: "stage whisper," when it's a noun, is two words. "She spoke in a stage whisper." However, when you look that up in the dictionary and scroll down to where it shows the verb form, we see that it's hyphenated. "She stage-whispered."
I also keep Google up. Any time I have a question, I just pop that puppy right in and find whatever it is I need to find. You can even type in "do you hyphenate stage whisper," and up will come information. There's no reason not to know the answers.
There are also some great websites that are fabulous resources. I recommend:
And just for fun, you can sign up for daily writing tips here.
Just remember - learning is fun. Knowledge is power. And this journey's exciting.