a. First, all the carbon atoms are placed at the junctions, and the bonds' terminals are represented as straight lines. Then, hydrogen atoms are fixed, bonded to carbon atoms such that the tetra valency of the carbon atoms gets satisfied.

Carbon and hydrogen atoms on Menthanol
b. All the carbon atoms are placed at the junctions and the terminals of the bonds. Hydrogen atoms are placed to satisfy the tetravalency of all carbon atoms.
According to the tetravalency, carbon atoms having a double bond will have fewer hydrogen atoms attached to them.

Carbon and hydrogen atoms on Ethambutol
d. Appropriate numbers of carbon and hydrogen atoms are placed on the ring. And then, lone pairs are added to heteroatoms.

Carbon and hydrogen atoms on Estradiol