One thing you might want to try is cross-validation (http://en.wikipedia.org/wiki/Cross-validation_%28statistics%...). Cross-validation should help you determine if your model is overfitting, as it will perform significantly better on its training set than on the left out data.
One thing you might want to try is cross-validation (http://en.wikipedia.org/wiki/Cross-validation_%28statistics%...). Cross-validation should help you determine if your model is overfitting, as it will perform significantly better on its training set than on the left out data.