1. Good hosting
Your site should be accessible 99.9% of the time and you need reliable support when things go wrong. Automatic backups are a bonus.
2. Professional theme
There are many theme design companies. Choose one that keeps up with WordPress updates and have a dedicated team for support. Oh and the theme must be simple. If you need 2 days to learn how to use the theme options and frameworks, that would defeat the point of WordPress.
3. Free plugins
There are thousands of plugins available to enhance and improve WordPress and the majority of them are free. But don’t get carried away! Only install what you need. One to start with should be Jetpack.
For a great in-depth article on this topic, head over to Elegant Themes.