Method one: save the wallet.dat files
It is pretty simple:
First encrypt the wallet.dat files(Winrar is the easiest encryption method),then copy the files and save the copies in your computer,USB flash disk or online cloud storage. Remember to take a new backup when your wallet have over 100+ translations,otherwise your BTC may lost.
Method two: Use brain bitcoin wallet
The only thing you need to remember is the password which can be used to generate the wallet address and private key,the advantage of this method is that you don’t have to save or remember private key
Method three: Use paper bitcoin wallet
Paper wallet means you can print the bitcoin address and private key on a piece of paper.Paper can be stored for a long time if you are careful