You need to follow below steps for Secure FTP Password :
a)First remember to “Sign Out/Log Out” from any of the “services”
b) Use strong, long and a complex password, as more variety of characters that you have in your password, the harder it is to guess the password.
c)Avoid sequences or repeated characters in your password.
d)Use Mix letters, numbers and symbols, and use case sensitivity.
e)Avoid dictionary words in any language.
f)Try to memorize the password, and avoid writing it down.
g)Avoid using only one password for all your accounts
h) Last but not the least is to change cPanel / FTP passwords most ofently