how to find hybridsation
Answers
If you can assign the total electron geometry (geometry of all electron domains, not just bonding domains) on the central atom using VSEPR, then you can always automatically assign hybridization. Hybridization was invented to make quantum mechanical bonding theories work better with known empirical geometries. If you know one, then you always know the other.
Linear - sp - the hybridization of one s and one p orbital produce two hybrid orbitals oriented 180∘ apart.
Trigonal planar - sp2 - the hybridization of one s and two p orbitals produce three hybrid orbitals oriented 120∘ from each other all in the same plane.
Tetrahedral - sp3 - the hybridization of one s and three p orbitals produce four hybrid orbitals oriented toward the points of a regular tetrahedron, 109.5∘ apart.
Trigonal bipyramidal - dsp3 or sp3d - the hybridization of one s, three p, and one d orbitals produce five hybrid orbitals oriented in this weird shape: three equatorial hybrid orbitals oriented 120∘ from each other all in the same plane and two axial orbitals oriented 180∘ apart, orthogonal to the equatorial orbitals.
Octahedral - d2sp3 or sp3d2 - the hybridization of one s, three p, and two d orbitals produce six hybrid orbitals oriented toward the points of a regular octahedron 90∘ apart.
I assume you haven't learned any of the geometries above steric number 6 (since they are rare), but they each correspond to a specific hybridization also.