Choosing an Executor is one of the most important decisions you will make when doing a Will.
It isn't an easy choice, because this person will be in charge of your money and family when you are gone.
They need a good mix of talents because they have to do a lot of things with financial and legal overtones, they need to be honest and moral enough to handle your money, and they need to be diplomatic enough to keep the family and your beneficiaries satisfied and happy.
It's a tall order. Sometimes, there is a simple answer, such as your wife or the primary beneficiary. Or, it might be your brother the Lawyer or your sister the Accountant.
If there isn't a clear choice, things get difficult fast. Do you want a friend to do it, or perhaps a relative that really doesn't have the skills? Or maybe your brother has the skills but the family is at odds and using him would inflame things. Or should you go the paid Executor route and hire a Bank, Trust Company or Lawyer?
For many important considerations and a more detailed discussion see Choosing an Executor.