Tagging helps to organize and share our online information with others. By attaching one or more keywords to a Flickr photograph, for example, we group it together with others that have the same tag. Hashtags serve a similar purpose on Twitter, the social micro-blogging service. The aim is to bring some order to Twitter users' published updates ("tweets") and make it easier to follow a topic of interest. And you don't necessarily have to be a Twitter user to get a benefit from hashtags.

How to Use Hashtags

1. Follow the @hashtags Twitter user (http://twitter.com/hashtags). It will follow you back automatically, and this enables the service to recognize and index your hashtags.



2. Create a hashtag by adding a hash symbol (#) to the front of an appropriate keyword as you write your Twitter update (for example, #nptech).



3. Track the tagged conversations that interest you. Twitter updates that include a valid hashtag are indexed at Hashtags.org, organized by tag, and available as individual RSS feeds. This means that you don't have to be a Twitter user to follow the conversation — it's visible to anyone.



Note that each hashtag index has its own web address and feed, distinguished by a word at the end of those URLs that matches the hashtag keyword.

The nptech tag is often used on other platforms to tag content related to nonprofit technology topics, and this has started to show up as a hashtag on Twitter as well.

Whenever #nptech is used as a hashtag in a Twitter update, that update will be automatically added to http://hashtags.org/tag/nptech/ -- and the corresponding RSS feed at http://hashtags.org/feeds/tag/nptech/.

You can choose to subscribe to the RSS feed for your favourite tagged Twitter updates,  such as those that have been tagged with #nptech.

That will send any new #nptech-tagged updates from Twitter to your favourite news reader (e.g. Google Reader, Bloglines, etc.).

As well as subscribing to an RSS feed for any tagged Twitter topic, you can re-publish the feed on your own website, archive it for future reference, combine it with other feeds to make a custom feed — and countless other possible uses.

Less is More

Hashtags are community-driven, so their ability to deliver what you're seeking will be determined by how effectively the community chooses to use a tag.  For example, #sandiegofire set the standard for the use of hashtags by a Twitter group to track news of a major catastrophy and to mobilize real-world resources to help those affected.

That said, not all Twitter users are welcoming hashtags with open arms:
"What's #irritating about #this sentence?" 

Dave Coustan's position is that Twitter should be about human conversation, not about writing for databases. "Imagine what Flickr would look like if all of the metadata was visually stuck to your photograph," he says. "Or what your blog would look like if you had to have a character before every word in your text that was also a keyword. Ick."

Certainly, as with any social-tagging system, hashtags have a potential for overuse and abuse that could dilute the effectiveness of any particular tag. Because the hashtags user must "follow" another user in order for that user's hashtags to work, however, a spammer or michief-maker could be "unfollowed" and thus dropped from the index.

Hashtag etiquette is still evolving, so let good social manners be your guide. It is a rare "tweet" that deserves a hashtag, so tag only those updates that you feel will add significant value to the conversation. One hashtag is best — two are permissable — but three hashtags seem to be the absolute maximum, and risk raising the ire of the community. Tag sparingly, and with careful discretion.