I have posted something similar way back when, but as the use of Twitter and hashtags has, like most other social media channels grown over the last couple of years, it is worth posting again.
Now I make no claims to being a Twitter/Hashtag expert, far from it. So in lieu of actual hands on information, I have gathered the best information I could find on the subject. So a special thanks to the folks at Hashtag.org for helping a girl out!
A hashtag is simply a phrase or keyword that is preceded by a pound (#) symbol and used by the micro-blogging community to create a thread of conversations around a specific theme or topic.
The purpose of the hashtag is to categorize topics, bring ideas together, inspire exchange and encourage others to join in. And because the conversations under hashtags, or any other part of the social networking community for that matter, are not regulated, micro-bloggers have more freedom to express what they want.
This is why hashtag usage is very popular in the likes ofTwitter, Instagram, YouTube, Pinterest, Google+ and other social networking platforms that read hashtags. You can find a list of the most popular hashtags at certain times atHashtags.org.
Limitations on Hashtag Characters
You only need to add a # before a word to make it hashtag. However, because a Tweet is only limited to under 140 characters, the best hashtags are those composed of a single word or a few letters. Twitter experts recommend keeping the keyword under 6 characters.
Use only numbers and letters in your keyword. You may use an underscore but do this sparingly for aesthetic reasons. Hyphens and dashes will not work.
Hashtags do not support spaces. So if you’re using two words, skip the space. For example, hashtags for following the US election are tagged as #USelection, not $US election.
No Special Characters
Hashtags only work with the # sign. Special characters like “!, $, %, ^, &, *, +, .” will not work. Twitter recognizes the pound sign and then converts the hashtag into a clickable link.
Don’t Start With or Use Only Numbers
Hashtags like #123 won’t work, so don’t use only numbers. Similarly, #123yo doesn’t work. But numbers are great for recurring events like #conference2012 or #SXSW12.
Be careful with slang
Slang words can mean different things in different countries, so be very mindful about the words you use. Effective hashtags are those that are concise, direct to the point and very relatable across cultures.
For a hashtag to serve its purpose and generate a following, don’t pepper your post with more than two hashtags. Overuse is annoying and defies general social media etiquette. You don’t want to be accused of being a hard seller, don’t you?
Read more are about hashtags in Why Use Hashtags?