So we all know we're supposed to have a different password for every site we go to, but of course no one does that. Instead you end up using the same password for everything because its easier to remember. The problems occur when your favorite website, knittin-for-kittens.org, gets hacked and your password stolen, and its the same password you use for your bank account.
What you need is a password scheme that lets you use a different password for every site you go to, so even if one gets stolen, it won't comproise all your other sites.
Here's the system I use:
Chose a random, nonsense "base" with both numbers and letters. Include at least one capital letter. For example: zh2Ms.
This is just something you will have to dedicate to memory. If you base it on a phrase, that can help. Example: zebra have 2 Many stripes = zh2Ms
Next, add on the name of the site or service you are using. For example...
and so on. Now you have unique passwords for every site you use, but you will always be able to remember them.
PS: for the best security, you should really be using lastpass! It's wonderful and free.