I second you for the importance of teaching others how to use twitter especially for professional development. I totally agree that the best way to teach twitter is to make your students practice using it. Asking them to perform different tasks on twitter is just what they need. I like your ideas and I think that they will work well. I just would like to point out that one of the challenges that people face when they newly use twitter is how to re-tweet and write a new message with hash-tags (especially if they created a group for their class) , so I believe they need to practice it in class.
There was that word that captured my thinking while reading through the post and triggered my imagination for ideas about using twitter …. ” a creative thing” … I am thinking that you can ask your students to take a photo of something they saw in their lives, search the internet for a pic., a video or an info-graph that is unrelated to education ( or their major – I am just mentioning education here as the example), create a link between that thing and education, and post it on twitter with a sentence describing how they find this thing related to education. It can be related to a solution for the problems of education, a deep reflection on teaching, the subject they teach, a student in their classroom, or an incident that changed their lives. I don’t know … they can even compete against each others to guess the relation of others’ posts to education before posting their sentences. They will help them use their higher-level thinking skills.
Another idea that crossed my mind is assigning students to re-tweet articles they liked with incomplete sentences describing it and the rest of students should read the article to reply with the best words completing these sentence.
Just a couple of ideas that I wanted to share …. hope you find them inspiring.