I recently posted this tiny post on how to delete remote tags from a Git repository. http://himer.us/kY2imV
I always have the problem (with my Drupal repositories) that I will accidentally send a tag labeled like: 7.x-3.x-beta1, and it should actually be 7.x-3.0-beta1. Every time I needed to try to replace that tag, I was having to search the internet again for the exact syntax to remove those incorrectly named tags from the Drupal repository.
I'll likely be trying to post a lot more git tips and tricks in the near future.