I use this method as do most of my clients.
I use the same basic password everywhere ie:
fluffy1 This will be used everywhere.
If you add a 3 character prefix to it that is based on the website you are at: Xxx
fluffy1 assuming Fluffy is the name of your cat.
Amazon would be Ama
fluffy1
Pizza Hut would be Piz
fluffy1
For further security at important websites, add a special character or two
Wells Fargo would be Wel
fluffy1!
Apple/iCloud etc App
fluffy1!
I developed this protocol so passwords would be easy to enter on the iPhone, and you will never need to write them down, since, you know your main password, and the prefix is whatever site you are at.
Always start with an upper-case letter-then the phone shifts to lower case.....Then "flip" to the number screen and enter 1-3 numbers....then, in the same screen you can easily use $!? as one or more special characters. (you should stay consistent on everything).
Admittedly, this is not the most super secure way, but it is much more secure than writing passwords down.
When writing down passwords, always underline upper-case letters and write the current date after the password, so you know which one is the current one. Do not use the date inside the actual password.
FYI-Notes App on Mac and iOS, now has the ability to password protect individual notes-put passwords there. I recommend using the unlock code for your iPhone to unlock your note. Always use Apple Keychain.
Here is a presentation on passwords, I recently gave to our 1400 member Apple User Group.
https://www.youtube.com/watch?v=0RQyp2k9nmc
PS: Bonus tip. When you enter your credit cards in Safari autofill, name the card with the expedition date and 3-4 digit security code in the name of that card, so when it autofills in Safari, you will see the expiration and security code without having to go get your card. Again-your decision on Security vs Convenience is your call.