An easy way to back up a cryptocoin wallet is to use the “backupwallet” command from the debug window console. This can be used like: “backupwallet ~\wallet.dat” in most wallets, by providing a path and filename to where you want the backup file to be made. You can run “help backupwallet” in the console if your having troubles.
Additionally most wallets include a menu command that will allow you to easily backup a wallet. Look for something like “Backup Wallet…” from the “File” menu.
You can also just copy the “wallet.dat” file directly from the hidden folder where it is stored. On a Linux system this would be a hidden directory in your home folder. Look for something like “.magi” for example for the Magi coin (use control-h to show hidden files)
About the Wallet.dat File
The “wallet.dat” file contains an initial pool of addresses with both public and private keys when the wallet application is initially started. It has transaction records and records of addresses kept in the addresses book. The transaction records can be recreated from the block chain.
If this file is not in the hidden directory when the wallet application is started the application will create a new file. (You can move the file around or rename it if you want to store your coins in multiple wallets)
Other ways of Backing Up
You can also use the “dumpprivkey <address>” command from the debug window to get a copy of your private key. If you have this key you can use it to restore all your coins in a new wallet if the old one ever gets lost or corrupted. (This can also be a good way of moving your coins to a new wallet without losing the coin days or paying a transfer fee.)
When to Backup
If you create lots of new address you might need to make a new backup of the file, however, most people end up storing their coins in very few addresses. If you add new addresses to the address book that you need to keep track of, you should make a new backup.