Plotting the predicted values against the real values in the holdout set is the best way to examine regression data. In ideal circumstances, the points should lie on a 45-degree line going through the origin (y = x is the equation). The better the regression, the closer the points are to this line.
Bring up your data in SPSS and select Analyze –> Regression –> Linear to thoroughly test the regression assumptions using a normal P-P plot, a scatterplot of the residuals, and VIF values.
