In addition to the other posts it is wise to have passwords that are obscure. Don't use words that conform to any language, especially English. This means not using your nickname or part-thereof, the words "password" or "security", the channel name, your dog's name, the name of your street or relatives or the brand name of your family's motor car. Passwords (for, both nicknames and chatrooms) should be hard for people and "channel hacking" scripts to guess. With a script it would be deemed probable to crack about 1/3 of passwords simply because most don't realise that the problem exists.
Using a combination of lower and upper case letters with numerals and ASCII characters like $#%^&*@, etc is the best kind of password and the method I use personally for nickname, any channels I own and oper password. Naturally, the longer it is, the better too and my personal preference is for passwords around the 15 character mark because I am bloody paranoid about these things.
Eight characters is a good start but if you can remember a longer password then use it. The easier you make things for yourself, the easier you make life for the occasional luser that likes to steal things.
