To make the house last house, glue all joints before you nail them. Galvanized nails won't rust and screws and hinges will hold the box together as it ages. The inside of the house should be rough. This makes it easier for the nestlings to climb out. Adding a couple of grooves below the exit hole helps.
Gourds make wonderful bird houses.
They 'breathe', making for a comfortable environment. They also sway in the wind making them undesirable to Starlings and House Sparrows. Adding a coat of polyurethane or exterior latex on the outside only, will add years to the life of the house. Avoid metal houses such as aluminum because they can become very hot in the sun making for an uncomfortable, if not deadly, interior. Don't use wood treated with stains or preservatives as the fumes could harm the birds.