basicly, if the first letter is a consonant, take the first letter to the end and add -ay to it. if the word begins with a cluster of consonants, move the grouping to the end and add -ay. if the word begins with a vowel, just add -ay.

here some more reading

http://www.ehow.com/how_4670_speak-pig-latin.html

http://www.potbellypigpets.com/piglatin.html

if you do a google search you can find more info.