Your birth date, wedding anniversary, phone number, and home address are obvious picks, so just do not use them.  Instead, think of numbers unrelated to major events and addresses in your life to create your PIN.  One technique that works for PINs is to divide them into two groups of two digits and treat each as a year - so that, say, 8367 becomes 1983 and 1967 - and then find some event that corresponds to each year. Each event should be something personal, known only to you, or something historical but relatively obscure. From these, devise an amusing and odd phrase linking the two events, from which the events themselves, and thus the dates, cannot be easily deduced. Write down this phrase rather than the PIN itself. Another way to create a PIN that is also easy to remember is to translate a word into numbers (like on a telephone keypad). Ex: Wiki would be 9454. ATM keypads often have letters printed alongside the numbers. Don't keep the same PIN for all your cards. Have a different PIN for each one, so that if you do happen to lose your wallet, it will be much harder for the PINs to be cracked.

Summary:
Choose a PIN password that is not obvious. Vary your PIN on different cards.