For Trending a Topic

From all the information I've been able to gather, none of which I knew before now, for a topic to trend it has to

• Be new. Meaning it can't have been used prior to the day it trends.
• Be original. RT's help a little, but for every new item with a particular #hashtag, the trend gets noticed.
• Be widespread. A topic can trend locally in small areas, but won't show up in the Twitter main trending topics. The more people creating original tweets with the hashtag, the better.
• Be relevant. Complete sentences work best, and not just a tweet of the #Hashtag.
• Be long lived. A topic trends both for being new and for being consistent over a period of time.

This isn't a perfect analysis. If you know more, please feel free to add info in the comments section!