How is hybridisation of a carbon atom determined by looking at the molecule's structure and observing the lone pair and/or sigma bond present?

Question

How can I judge the hybridization of a carbon atom of any carbon containing compound just by looking at its structure? How can I say this by the help of lone pairs and sigma bonds present?

Answer 1

The answer you are looking for is probably this:

Count the number of $\sigma$ bonds made by that atom, and add to that the number of lone pairs present on that atom. This number is called the steric number.

If the steric number is $2$, hybridisation is $sp$. Similarly, $3 \Rightarrow sp^{2}$, and $4 \Rightarrow sp^{3}$ hybridization.