I have never used Tumblr before, but I started taking some notes of things I think are important to getting your new blog found and hopefully get people to share your videos.
In this Hot Blog Tips Hangouts on Air, I go over some tips that I am finding while using Tumblr!
Watch on youtube.com
Hope this gives you a few ideas if you are new to Tumblr!
You can see a few of our blogs at http://hotblogtips.tumblr.com/