Auto Categorization of documents

Can you guide me in auto categorization of documents.

So, in DB we have a lot of long description of ticket data ( email conversation, or resolution data etc) , i need to train the classifier such that any new incoming ticket should be auto categorized to the right category.

STEPS TAKEN till now.

1) Tried to do unsupervised learning, to form clusters of words.

2) Used Naive Bayes classifier, but here I have manually labelled the training data set.

Any way which you can suggest in which I can do auto labelling of the text which can be used as training data.

Eagerly looking for your help.