You may (or may not) be surprised to find out that the three most common passwords are 123456, password, and 12345678. Dont use those. The ideal password is a random collection of letters, numbers, and some symbols, but thats not a password that most people will be able to remember. To simplify things, a good rule of thumb is to include at least 1 number, 1 uppercase letter, and 1 symbol in whatever word(s) you choose to use.
