Hijackers use increasingly sophisticated password ''crackers'' in an attempt to gain unauthorized access to accounts.
In order to make a password as strong as reasonably possible it should be at least 8 characters in length and contain at least one each of the following:
Upper case letter
Lower case letter
Number
Symbol [ @,#] etc.
This doesn't guarantee that a password can't be cracked but it makes it more difficult.
Also - needless to say - NEVER give your password to anyone.