What is a bad password?
Your name, name of someone from your immediate family, any information that can be looked up on your Facebook or any other social network site.
What is a really bad password?
12345, abcde, asdfg, a11111, abc123, etc. These passwords are unfortunately common and are very easy to guess.
What is a really, really bad password?
Name of site with or without number. facebook or facebook123 is about the worst password you can choose for your facebook account. These passwords are even more common and you might as well leave the password blank.
Are good password hard to remember? I say no. I recommend picking two words, at least 5 characters each, preferably not English and if English is not your native language, don't use that language either. Pick each word from a different language and these words should not be greetings or curses. Replace vowels with numbers and symbols. For example, "a" can be 4 or @, "i" can be 1 or !, e can be 3, o is 0. You can do same for some of consonants. "w" can be vv or \/\/, "l" can also be 1 or !, "k" can be |<, etc. Make the first letter of the second word a capital.
Now you have a password which is easy to remember and very hard to crack. Microsoft has a very good password checker which you can use to check the strength of your password.
One last important point. Don't use the same password for different sites. Your email should have a unique password. Social network site should at least have another password. Financial sites should have a third password, though preferably a different one for each site.