Evaluation is a very important part of your practical work in Media Studies. It should be an ongoing part of your production process, and not just some quick thoughts scribbled down at the end. Don't be afraid to make both positive and negative comments about your project as a whole. Highlight elements you're pleased with as well as commenting on aspects that didn't turn out so well. An honest, thoughtful evaluation is essential for a top grade.
In your written evaluation, you have to demonstrate an understanding of the process you have undertaken and how that compares to real industry practice, whatever your production may be. This is where good planning and research during your pre-production phase is invaluable – how much do you know about how the professionals do it? If you've studied industry practice, and can make references to real media productions (use plenty of examples!), you'll be able to show that you have a good understanding of the media form you were producing. Your initial research will also help prove that you had a definite target audience in mind throughout the process.
You need to critically examine your finished work, be aware of where improvements could be made, and suggest ways you would do it differently next time. How have you learned from your mistakes? What do now you know about the technological tools you used that will change the way you work in the future?
You should state your original aims (did you achieve them? If not, why not?) and briefly describe the process you underwent (explaining the creative decisions you made and the problems you encountered) when establishing those aims.
Your evaluation should also include careful consideration of the following:
Make sure you know how many words your evaluation should be, and stick to the limits. Throughout, your language should be formal and use specific media terminology. Use the glossaries elsewhere on this site to help you.
And, finally, as with any piece of work, PROOF READ every sentence carefully before you turn it in!