  The spatial and the angular variants of the Goos-H\"anchen (GH) and the
Imbert-Federov (IF) beam shifts contribute in a complex interrelated way to the
resultant beam shift in partial reflection at planar dielectric interfaces.
Here, we show that the angular GH and the two variants of the IF effects can be
decoupled, amplified and separately observed by weak value amplification and
subsequent conversion of spatial$\leftrightarrow$angular nature of the beam
shifts using appropriate pre and post selection of polarization states. We
experimentally demonstrate such decoupling and illustrate various other
intriguing manifestations of weak measurements by employing optimized pre and
post selections (based on the eigen polarization states of the shifts)
elliptical and / or linear polarization basis. The demonstrated ability to
amplify, controllably decouple or combine the beam shifts via weak measurements
may prove to be valuable for understanding the different physical contributions
of the effects and for their applications in sensing and precision metrology
