Passwords: whether you're trying to gain access to your friend's tree-house or your bank account, you will need the correct password. But what's the best way to pick a password? If you look at the keyboard on your computer, you will notice several keys. Most of them have one letter on it. Some of them do not.
If you are making an all lower case password, that means that each time you press a key that password gets 26 times better, every time you press a key. But it doesn't stop there! You can hit the shift key some! Every time you do that, now your password is fifty-two times better! And there are all those other keys! You can make your password almost a hundred times better with every keypress now!
If you are only making an 8 or 16 character password, that is still not very good. "But I used '~'! Nobody knows about '~'! And my password is 'totally random'!" Computers know about '~' and most likely, a computer will be guessing your password. Computers are also better than you at being "random".
Now, if you have a dictionary handy, and it is a good one, it should have more pages in it than you have letters on your keyboard. And each page will have multiple words on it! What if you were to pick four entire words out of the dictionary? Now you only need to remember four things! And your password should be over 16 characters long! And you can still use '~' somewhere! Take that computers!
Check out passphra.se to get a better password. If you are sysadmin, this is also way less frustrating to users than when you switch their password to a Game Genie code.
Another good option if you are a huge nerd is the "diceware" method of generating a password.