Obviously, it is very early days, but it will save time later if you get into some good habits when researching for your critical investigation.
Everytime, you find a source, be sure to reference it after your notes, because when you come to write the essay, you must acknowledge every bit of information you use.
If it is a book, record the source like so:
Davies, Luke ‘New Media’ (Puffin Books: 1999)
For websites, of course write the website address, but also try and record the author and date it was written.