The best thing to do is to have a two-way authenticator or store these coins offline . Even virus in your computer cant penetrate if you use these kinds of method.

Here are some method on where to store it using offline method. This is the safest way though.
1. On a USB drive or other storage media
2. On a Paper wallet
3. On a bearer item such as a physical bitcoin
4. Use a offline Bitcoin Hardware wallet

Step 1 — Create a bootable USB flash drive.
Step 2 — Create a cold wallet.
Step 3 — Create a “watch-only” wallet in the main OS or mobile phone.
Step 4–Spend Bitcoins in a secured way.

I summarized the context from this blog : https://goo.gl/aZn2kg
If you want to learn more just visit the link.