Hashtags are a quick, convenient, and useful way to make your important keywords stand out. Made popular by Twitter as a way of search enabling and categorizing your short posts, hashtags are much more useful than you might think. Delimiting a tweet with a couple of hashtags can greatly improve your visibility and findability, and there’s also many other ways to use a hashtag that you may not consider:

• Creating your own, made up hashtag is a great way to categorize your tweets for future re-purposing. For example, if you frequently tweet about something special, perhaps Colorado micro brew, if you make up your own tag like #glennCObrew it will likely be unique to just those tweets that you post about the specified topic. then you can use a 3rd party service like paper.li to build a summary of those posts and organize them into something a little more fun.
  
• When you post a tweet consider using a couple of hashtags to mention key topic areas that apply to your post. this will help others who may be searching twitter for the hashtag term – I suggest only using common terms and buzzwords.
• It has been proven that twitter posts that contain hashtags get more re-tweets. Include a relevant hashtag and you’ll be more likely to reach new followers or potential followers and you will definitely notice more retweets. Hashtags are likely the best way to reach people that you are not yet connected with.
• One of the most useful ways to use hashtags is for events. When attending, organizing, or following an event of any kind a hashtag is crucial! Event planners need to keep this in mind and from the start should have an “official” hashtag and promote it all over the place! If an event organizer doesn’t create an official hashtag the community will do it and typically what will happen is several hashtags will eveolve and the conversations will be re-routed in a number of directions – a real annoyance. Hashtatgs should be used not only for conferences and official events but can be used for any event for that matter, a webinar, social meetup or tweetup, etc…
• Do you author blog posts, publish feature articles or even release PR/press releases? Consider including hashtags at the end of your post for added inclusion and ehnanced SEO. I would also suggest, if you have room, when creating a subject line for an online article or PR release include one hashtag at the end of the subject for a little more oomph!
• Use hashtags when using other social services also. For example, when posting a photo to instagram, include a brief description with your photo but also add on a couple of applicable hashtags. Instagram hotlinks #hashtags so they will be hyperlinked and relveal other related photos on Instagram.

See more about hashtags:

• Looking for additional information about hashtags and tips about common hashtags? Check out http://www.hashtags.org. Its never a bad idea to tweet about trending topics in order to get added Klout on Twitter!
• Twitter support  about hashtags
• Why use hashtags
• Hubspot, how to use hashtags
• Twitter Shortcuts
• Twitter Best practices and tips