1. Google Authorship
2. Citations
3. Content
4. URLs
Make sure your site URLs are absolute and not relative in your code. They shouldn't be too long and contain multiple query parameters. If they need to be rewritten, you have rewritten them.
5. The Alt Attribute
Use this tag properly, but use it. It belongs on every image on your site (sometimes it will be empty).
6. Page Speed
Check your site on the Google Page Speed tool. Speed matters especially in mobile. Get your site score above an 85-90.
7. Robots.txt
Your robots.txt doesn't block your web page from being indexed, only crawled. If you want to block a page from being indexed, leave it off the robots.txt and add a noindex tag.
8. Penalties
If you try to recover your site and you fail the first time, get an expert to help you. Google penalties are tricky subjects. You may not know enough about penalty recovery to get your site out of penalty status.
9. New Sites
There is only one way to really make sure Google won't find your new site: lock it down with a login. Robots.txt don't prevent site indexing and Google doesn't need a link to find you. If you don't lock it down, don't be surprised when your new site is indexed before you wanted.
10. Get a Site Audit Every Year
There are so many new aspects of SEO in the past two years that it can be very difficult for the average business owner to keep up. Add to these changes the number of simple penalties a site can receive and you can be quickly over your head.