Depends if your site is high risk. If your site/subject is "hated" then expect DDoS attacks, you can protect them using hardware firewalls. Certain companies offer these. Use a well coded script, so you are safe from SQL Injection. Like a paid CMS or Joomla, or just use a html website if you don't need PHP. Choose a good hoster that is secure and doesn't use Apache, as that is vulnerable to Slowloris. Somthing like Varnish or LightSpeed will do the job.

I hope I helped you.

Michael,