Hi.
Preventing ddos atacj can be do it using severals techniques like:
a) Using webs server security modules like apache mod secure or using restrictive web server like nginx or lighttpd
b) Using some tools like firewall for example, iptables with restrictive rules for avoid ddos
c) Using tools for preventing ddos like fail2ban
I you're using a site worpdpress or drupal based, I can migrte it to your VPS and secure it for avoid ddos without problem
I've worked into computer security for a lot of years.
Open to questions