I guess the concepts i'd promote would be similar to the advantages of blogging which i've already spoken about. I'd stress that blogging is a great way to channel and communicate your thoughts, and to keep track of things you've done day to day, books/music/films you've enjoyed, and cool websites you've found. Also, blogging helps to hone your writing skills, and involves you in a university 'community'.
How to market it…? Hmm. Well, I guess the students would need to be made aware of the blog site, as well as possible. This could include someone talking to them about it on their induction days, fliers and billboard notices, and a link to it on the main page of the general Warwick uni website. Perhaps it would also be useful to have student blog representatives who could talk to new students about it, and pass it on by word of mouth?