Meiosis and sexual reproduction

Eukaryotic cells can be divided by mitosis or meiosis. In humans, mitosis generates new cells for growth and repair; meiosis generates sex cells (gametes) termed as sperm and eggs.

However mutations are the eventual source of genetic variability, both meiosis and sexual reproduction as well can contribute to new genetic combinations in offspring.

Question: How do both meiosis and sexual reproduction (that is, fertilization) generate offspring which differ genetically from the parents? Be sure to talk regarding steps in meiosis which raise variability and also the procedure of fertilization.