How to get users to create more secure passwords

Strong passwords are the first line of defense against hack attacks, but how can you get users to create passwords that are complex and don't contain any dictionary words, without making the passwords so hard to remember that they end up writing them down? A random combination of letters and numbers (such as rjfoo3B7p2) is ideal, but hard to remember. A handy trick is to have users create password phrases or sentences that include numbers and then reduce them to abbreviations. In other words, I love my two cats, Susie and Fluffy, becomes Ilm2cS&F, which looks like a random group of characters but is much easier to remember.