Avoid No Visible Contact Details
Being Mobile Friendly (1)
Fast load page(2)
Your website needs to have a clear and concise message. Underlining the goals of your website will help you pin down your hierarchy and reading order.
Avoid Designing Cluttered Pages with No Whitespace.
This follows on from not having a visual hierarchy for your website.
Avoid Overly Complicated Forms
Understanding Basic SEO
Providing an Email Opt-In Form