2: Backups, lots and lots of backups. And update the backups EVERY time you do a transaction!!!!
3: Keep your coins in multiple "batches", so if you lose one, you don't lose all.
4: Keep most of your coins offline. A bootable USB key is a good idea to reduce hack surface. Divide up the coins on multiple removable USB keys that you normally keep removed. (And USB keys can and do fail, so don't forget those backups.)
5: If you encrypt your wallet write the password down!! Your attack vector is hackers on the internet - they can't see the postit on your wall (if they are in your house you have bigger problems). But your family will appreciate the ability to have the money in case of problems. (Or if you decide to not do anything with coins for a year or two, then want to get back into it - you'll probably not remember the password. There are far too many people who lost their coins because of encryption.)