Watch your spending on ads--they can be grossly ineffective. Use social media and generously interact with fellow writers and readers. Don't abuse FB and Twitter solely for the purpose of "Buy My Book." Join writing groups and learn from the pros. Ask politely for reviews--don't pressure, harass or intimidate. Be creative. Target your genre readers. Offer incentives and freebies. Craft a newsletter and send it out bi-monthly. Don't take critiques as personal attacks--learn from honest opinions. Don't despair. Never give up. Revenge query.