I dont read Digg much, but for anyone that does is there a general type of post that really attract the 'diggers', or certain subjects that do more than others?
Its a matter of posting it at the right peak time, content that is original, current or breaking news don't worry about the subject so much. Something that will catch the attention of the audience or make them say "wait a minute" before they click on it to read some more. An odd or cool story works good and has to be original.