International Talk Like a Pirate Day has a website...it can be found at: http://www.talklikeapirate.com/ The day is always on the 19th of September, whatever year it be, mateys!! Arrrr!

[edit] Steps

Get your pirate costume and assemble a crew. Involve friends and engage in pirate-speak with casual passers-by. (see Step 2)
Learn to Talk Like a Pirate (if you don't already know). Pirates talk in colorful manner - put on the manner of a pirate by muttering, and saying things like "Avast, ya scurvy varmints!"
Spend the rest of the day being piratey. Wearing a costume, talking to a stuffed parrot, putting on an eyepatch, these are all ways to spice up the pirate-y goodness of the day!

[edit] Tips

Mark your calendar so you don't forget!
Find yourself a good crew!! The more the aarrrrrr-ier!
Wear your flashiest jewelry and your loudest, most colorful rags.
Be very colorful while talking like a pirate. Arrrr!!!
Drink rum, pineapple juice, coconut juice, or other suitable piratey beverages.
Sing at the top of your lungs, even if you sound off-key or don't know all the words. Pirates love to sing!
Ignore people who give you funny looks. They're missing out on a great time.
To add to the mood, try listening to "piratecore" bands such as Flogging Molly.