The best way to properly back up your WordPress install is;

1) get and install http://wordpress.org/extend/plugins/wp-db-backup

2) secure a gMail address that will be used solely for database backups

3) configure the plug-in with your gmail address and set the schedule based on how frequently you post and how frequently you receive comments.

4) occassionally delete old backups from the gMail account.

Were you expecting more steps?...