If you are used to typing "wr" to backup your configs, Cisco has been working hard at making it less easy to backup your configuration to flash. For years I've heard that write memory is "going away" and that everyone should use "copy running-config startup-config". If you are working on some newer platforms (NX-OS), you might find that wr doesn't work unless you create an alias:
alias exec wr copy run start
But there are cooler ways to backup your configurations now (aside from using third party tools), such as the Archive feature.
To backup your configs using Archive, here's a script to backup your config to disk0 once a day for two weeks:
Router(config-archive)# path disk0:backupconfig
Router(config-archive)# maximum 14
Router(config-archive)# time-period 1440
If something happens to the config and you want to roll back to yesterday, that's where configure replace comes in: