Best way to redirect domain to www. (vice versa)?

First off, do I have to put www. in front of my domain when hosting a website? I know that both do the same thing, is it recommended practice to keep the www. or does it not matter? What would be the best way to redirect mydomain.com to www.mydomain.com, is it better to use the DNS server (BIND and Godaddy) or Apache? If it were in BIND, how would I edit my current forward lookup zone configuration?

$ORIGIN mydomain.com.
$TTL 86400
@   IN  SOA mypc.mydomain.com. info.mydomain.com. (
    2013071101 ;serial
    21600      ;refresh after 6 hours
    3600       ;retry after 1 hour
    604800     ;expire after1 week
    86400 )    ;minimum TTL 1 day

    IN  NS  mypc.mydomain.com.

    IN  A   EXTERNALIPHERE

    IN  MX  10  mail.mydomain.com.

mail    IN  A   EXTERNALIPHERE

www IN  A   EXTERNALIPHERE

mypc    IN  A   EXTERNALIPHERE

ftp IN  A   EXTERNALIPHERE

mc  IN  A   EXTERNALIPHERE

Would I change "www IN A EXTERNALIPHERE" to "mydomain.com IN CNAME www.mydomai.com" or is that in reverse? How would the reverse lookup look like?