Make your password longer. For a hacker with a computer that can make 1000 guesses per second, a 5-letter password like 'ftmps' takes about 3 hours and 45 minutes to crack, while a 20-letter password would take around 6.5 thousand trillion centuries.
Use a group of words written in lower case. For example, 'help cheese monkey swimming' is more secure than 'M@nch3st3r' because it is longer and harder to guess.
Try to make them memorable, like a phrase or a story that is easy for you to remember.