Model testing & validation?

predictive_model
validation
testing

#1
  1. How to Validate Predictive models.
  2. What is the SAS code for dividing datasets in traning, validation and test.
  3. Which statistics should I be comparing in these datasets to conclude if my model is good.
  4. what to do if the stats do not match for the train and validate models.
  5. what is the test dataset used for?

#2

only @Sunil can answer in an easy way