An alternative setting is to have the default virtual host at the end of the config file rather than the beginning. This way, all alternative virtual hosts will be checked before being matched by the default virtual host.
Example:
NameVirtualHost *:80
Listen 80
...
<VirtualHost *:80>
ServerName host1
DocumentRoot /someDir
</VirtualHost>
<VirtualHost *:80>
ServerName host2
DocumentRoot /someOtherDir
</VirtualHost>
<VirtualHost *:80>
DocumentRoot /defaultDir
</VirtualHost>