Backup Advice

So I am an average consumer who stores all photos/music/homevids/contacts etc on my 250gb hard drive. Recently i noticed when working with video the drive can get pretty full.

I have made some backups of photos on CD but would rather get an external harddrive to store backups of all the above and give some extra space for working with video.

Do I just get an external hard drive (firewire) and hook it up and copy stuff across to backup? Obviously when lepoard comes along time machine will do the work for me. I read poeple talking about the various RAID setups - do I need to use one of these or is that really for pro users?