  We analyze the decay processes B \to DK, DK^*, D\pi, and D\rho in a
model-independent way. Using the quark diagram approach, we determine the
magnitudes of the relevant amplitudes and the relative strong phase shifts. In
order to find the most likely values of the magnitudes and the relative strong
phases of the amplitudes in a statistically reliable way, we use the \chi^2
minimization technique. We find that the strong phase difference between the
color-allowed and the color-suppressed tree amplitude can be large and is
non-zero at 1 \sigma level with the present data. The color-suppressed tree
contributions are found to be sizably enhanced. We also examine the validity of
factorization and estimate the breaking effects of flavor SU(3) symmetry in B
\to DK, D\pi and in B \to DK^*, D\rho.
