
This is an fun and easy one. Just plug in your birthday (month, day, year) and then enter your Twitter username and password and you will have your horoscope, or Twittascope, tweeted to you every day.
One of the most popular ones (to date) is #followfriday. And also anytime there is a social media conference you can be sure there will be a hash tag. In fact, following people who are at a conference is almost as good as being there. People keep you up minute-by-minute of what is going on!
One last thing to note. If you want to creat a hash tag you should first find out if it isn't already being used. Search first, then post - Go to http://hashtags.org/ and search for existing hashtags in use.
If it is already in use you can leverage conversations that are already ongoing around your desired topic. And if you're interesting, they will follow you.
For more information, there is a really great article from Mashable on this.