1. On the master: `puppet cert clean <agent_certname>`
2. On the agent: `mv /etc/puppetlabs/puppet/ssl/ /etc/puppetlabs/puppet/ssl_bak`
 - Never do this if you are trying to regenerate the cert for the agent on the master.  Instead you would need to delete specific certs
3. On the agent: `puppet agent -t`
4. On the master: `puppet cert sign <agent_certname>`