The executor will be responsible for handling financial matters, they will need to communicate with professionals such as lawyers and with the beneficiaries, so it is a good idea to choose someone who is responsible and who you can entrust to act in your best interests.
This may be a close family friend or a family member who you believe to be reliable and honest. Difficult decisions may arise in the probate process, it is therefore important that the executor can respond to tricky situations and address them swiftly. In addition, an executor should be trustworthy, truthful, and genuinely want to do what is best for you according to your Will.
If you do not know any family or friend that would be suitable, you could appoint a professional such as a solicitor to be an executor of a Will.