Much depends on how you acquired the data, the model itself, the number of response variables and the type of factors in the model. One way to do this is to save the prediction formula in your data table. Select the Red triangle next to Response > Save Columns > Prediction Formula. Add rows to the bottom of your table and fill in the values you want and examine the Prediction Formula column for the answer. Often you can use the interactive Predition Profiler to move on the axis to the proposed input variable settings.
"All models are wrong, some are useful" G.E.P. Box