Here is a article that I recently read at Writersandauthors blog about common mistakes that authors do. I think these are very helpful especially when you have been in the business for a while.

1) No Marketing plan
Your marketing plan will help to keep you focused on your goals, save you time, and make it easier for you to analysis what’s working and what’s not.
 
2) Being too “me-centric”
Make it about them, NOT you. No one likes to be spammed with constant sales pitches. Instead build a marketing plan that offers value to your target audience. What benefits does your book offer readers? Why should they be interested in what you have to say?
3) Forgetting calls to action
Give your readers clear instructions about what you’d like them to do. If you want more reviews, ask for them. If you want people to share your link, ask them to share it.
4) Waiting to start marketing
If you wait until your book is published before you start marketing you’ve waited too long. Marketing should start even before you’ve finished writing the book. Build your author brand and create some pre-release buzz. Launching your book will be much easier.
To see more check out the blog link below