The rule of thumb to protect one’s family is to purchase enough to cover your annual income through retirement age. In addition you want to pay off your family’s home mortgage and any outstanding debts or educational expenses.
Once you determine the required face value of your insurance company, you can start shopping around for the right policy (and a good deal).
Obviously there are other people in your life who are important to you and you may wonder if you should insure them. As a rule, you should only insure people whose death would mean a financial loss to you. If you have a spouse or partner that also is a contributor to the family income, then it would make sense to go through the same exercise to determine the face value of the policy.