As I was reading about digital citizenship, one thing I think is very important to teach is to not believe everything you read. As I've worked with students, I've seen how they think because it on the internet it is true. Students need to understand that they should evaluate and analyze the source and also confirm what they read with several sources. This is true of anything in print and I don't think it's being taught as much as it should be.
Tied into this would be to teach how to access credible sources. Students should be taught to go to reliable data bases and taught how to access those data bases.
Of course, one important thing to teach at all times is safety on the internet. Many times students don't understand the internet can be a dangerous place to be as well as a good tool.
I liked Brain Pop from the Ed Tech website because it had many different topics for digital citizenship like online sources, safety, copyrights, etc. Almost all of the things I would like to teach were there.
Teaching digital citizenship should be an ongoing process that takes place all year. I would definitely start the first week of school by showing Brainpop on etiquette and safety. I would use each of the other ones as we had lessons that used technology, using whatever fit with that lesson. Brief reviews all throughout the year would reinforce all the information presented.
One way to share the idea of digital citizenship is on the syllabus that is sent home at the beginning of the year and ask for a parent and student signature. I would probably include something on my blog also.