[R] an off-topic question -> model validation

[Wensui Liu]

Currently, I am working on a data mining project and plan to divide
the data table into 2 parts, one for modeling and the other for
validation to compare several models.

But I am not sure about the percentage of data I should use to build
the model and the one I should keep to validate the model.

Is there any literature reference about this topic? 

Thank you so much!