I'm shamelessly copy/pasting my own tips from another post:

[-]doggocoin 25 · 21 hours ago
If you are going to use a wallet like this, for the love of all things holy, BACK IT UP!

Here are the ways I have my stuff backed up:

• Passworded zip file containing various wallets/keys
• The zip file is secured on a cloud storage service with a strong password and two factor auth
• Paper wallet printed, hidden from plain sight and stored at my parent's house
• USB drive containing the passworded zip I mentioned above, hidden in my apartment
• DVD disc containing the zip I mentioned above, hidden at my parent's house
• External hard drive with the zip file and a password blocking people from accessing the drive
• Do your usual due diligence and don't browse questionable sites or accept strange files, and if you do make sure you have a good antivirus
• Consider a hardware wallet, but your choices are limited as many altcoins aren't supported by them (yet)

I'm also using generated passwords (4Js*dS5fjI38, for example) on all my exchange logins.