Over whisking the eggs and other ingredients creates a lot of aeration and air bubbles that look very unpleasant.
Too much sugar can make the custard pie overly sweet. So, use the sweetener accordingly.
Sugar can coagulate egg yolks so do not let them sit too long together and to prevent this from happening strain it twice.
Remove from the heat as soon as you observe ‘barely set’ appearance of the custard pie.
Let the pie sit in the refrigerator for some time before slicing. This will help it to set and become firm.
As the custard filling is very wet, it is important to bake the pastry well to prevent it from breaking.