Here is a really useful blog how historians can make use of Twitter. It summarises well those 5 tools and gives examples.

The 5 tools are:

1. Follow organisations: get updates & research tips, highlights or additions to collections, get in touch with staff. These could be museums, libraries / archives, research instutions, history organisations, research group, etc.

2. Use hastags: to search tweets by subject, identify an interest group

3. Tweet a conference: share thoughts on talks, etc. with conference participants, great for networking

4. Share resources: new resources, recommendations, etc. are regularly posted.

5. Search for job

@HFLOxford is where we tweet updates about library services and collections for historians, new resources/books/databases, circulate news about tools for historians and generally pass on any news that makes lives for historians easy,  richer and keeps it up-to-date.

The full descriptions are at AHA Today: Five Ways for Historians to Use Twitter.