While the internet has been around for quite a while now, hash tags are fairly new. They are a way for us to find and connect with people who are having specific conversations on social media. As you will learn later in this post, they are used for having group chats (Twitter chats) but they are most used for categorizing.
When I am trying to connect with people centered around a specific topic such as #blogging or #podcasting, I will often go straight to Twitter. Then I will do a search based upon a specific hashtag. This helps me see who is talking about that topic and what they are saying. From there, I can respond to them or follow them. Essentially, hash tags can help you cut thru the clutter.

What is a hashtag?
A hashtag is a word with the # sign in front of it. For example, #blogging is a hashtag. It is a way to label a piece of content or sort it for easier search.
Hashtags are a great way to reach an even broader audience. People continually follow and/or search based upon hashtags. If there is something trending in the world such as the Super Bowl, entire conversations will occur because people sent a tweet that included #superbowl. People who may not otherwise connect wind up connecting, even if it’s just temporarily.
So if you’re an author and your book is a thriller, consider using the hashtag #thriller when tweeting about your book. The example below is a Tweet that I recently sent out of my personal Twitter account.
For example:
@ITeachBlogging Podcast: Should you summarize your #blog rss feed http://apple.co/1JzM74E <----What do you think?
[Ed. note: Someone outside of your network doing a search on #blog can see your tweet and comment on it.]
By the way, I co-authored a book on Twitter a couple of years back. Parts of the book are slightly outdated now but the parts on Hashtags and how to use them are spot on. This book is jammed with an actionable theory on how to use Twitter that never goes out of date.

Tips on How to Use a Hashtag
Don't use more than two on average. Anything more and the Tweet tends to be received as spammy.
Don't use a hashtag just because it is trending. Your hashtag needs to be relevant and I recommend that you use the same hashtags often. This will help you become known in a certain community. For example, #amwriting is a popular hashtags that writers will use to communicate that they are working on their book.
Google Plus
Google Plus has an explore section. https://plus.google.com/explore You can go here and find hashtags relevant to your topic. They will also show you trending hashtags, which can be quite helpful for finding new connections.
As a rule of thumb, use 2-4 hashtags on G+. My tip is to explore hashtags in your genre and then write down a list to choose from for the future.
It seems that the secret to Instagram is the hashtags. It is not uncommon to see people using 10 or more hashtags per post. There is a website that you can use to find the top hashtags on Instagram: http://top-hashtags.com/instagram/.
I added Pinterest to this list mainly as a discussion point. It appears that while you can use a hashtag in the Pinterest description they are nearly worthless on Pinterest. The best tip for using hashtags on Pinterest is to establish one for your specific brand and focus on that. For example, I should start using #BlogBuildTips when I pin my latest blog post. However, when I was reading up on this topic, most people did not see much value in hashtags on Pinterest.
Sources: http://www.socialmediaexaminer.com/increased-instagram-visibility/
One of the best uses of Hashtags that I have seen is on Twitter and related to events and Twitter chats.
During a conference people will connect and communicate with one another using a hashtag on Twitter. For example, when I went to Podcast Movement we used the hashtag #PM14 and #PM15. Now that the 2016 Conference has been announced people are already talking about #PM16 on Twitter.
Another great example of using a hashtag is in a Twitter chat. For a while, I was holding a Twitter Chat using the hashtag #BlogBuildTips. It was scheduled at a specific time on a specific day and we would talk blogging using that hashtag. If you are interested in finding a chat and joining in then you can check out this link: http://twubs.com/twitter-chats.
What are you some of your favorite hashtags? Do you use hashtags?
First let me say that I just found your podcast today and love it. I listened to your podcast on hashtags (above) and 2016 goal setting. I found both extremely informative. I appreciate how you provided clarity on hashtags in general as well as how they differ by social network. Looking forward to catching up on the archives on my way to work! Hope you get your voice back! :)