Correct project settings, preparation of footage, and initial composition settings can help you to avoid errors and unexpected results when rendering your final output movie. Before you begin, think about what kind of work you’ll be doing in After Effects and what kind of output you intend to create. After you have planned your project and made some basic decisions about project settings, you’ll be ready to start importing footage and assembling compositions from layers based on that footage.
The best way to ensure that your movie is suitable for a specific medium is to render a test movie and view it using the same type of equipment that your audience will use to view it. It’s best to do such tests before you have completed the difficult and time-consuming parts of your work, to uncover problems early.
Aharon Rabinowitz provides an article on the Creative COW website about planning your project with the final delivery specifications in mind.
For more information about encoding and compression options, see this FAQ entry: “FAQ: What is the best format for rendering and exporting from After Effects?”