I'm running a system that includes virtual servers which makes the setup a tiny bit more complex. Following the instructions above I get the following error message (in /var/log/apache/error.log) when I try to start the server.

[error] mod_ssl: Init: (www.xfly.co.uk:80) Illegal attempt to re-initialise\
SSL for server (theoretically shouldn't happen!)

This is fixed by including the lines that activate the SSL Engine in a virtual host declaration rather than in the main server definition. I think it has something to do with the way mod-ssl is compiled but don't quote me on that. Anyway an example virtual host declaration is show below (with a modified email address):

ServerAdmin webmaster@example.com
DocumentRoot /somewhere/crazysquirrel.com
ServerName www.crazysquirrel.com
ErrorLog /var/log/apache/error.log
CustomLog /var/log/apache/crazysquirrel.log combined

SSLEngine on
SSLCertificateFile /etc/apache/ssl.crt/www.crazysquirrel.com.crt
SSLCertificateKeyFile /etc/apache/ssl.key/www.crazysquirrel.com.key
SSLLog /var/log/apache/crazysquirrel_ssl.log
SSLLogLevel warn

The other problem you may encounter is not having Apache bind port 443. In your server configuration file (httpd.conf) you need to enter the lines:

Listen 80
Listen 443

If you enter only the second line Apache won't bind port 80 and your non-ssl websites will stop working.