Use Hashtags to connect your posts to popular ‘Categories’ within your social media.  If you had a hard day at work, poured yourself a glass of wine and snapped a picture of your feet, the wineglass, and the fire you might post something like this:  “My reward for a hard day’s work #wine #relax” 

Hashtag Basics:

• They always start with # and won’t work if you include any spaces, punctuation, or symbols
• Don’t string too many words together -- The best hashtags are short and easy to remember 
• Use relevant and specific hashtags -- They need to be easy to find by your target audience
• Limit the number of hashtags you use (More isn’t always better)

Why Use Hashtags?

1. Increased Engagement on Your Posts -- Using hashtags means you are taking part in a topic or conversation, and hashtags will make your posts visible in that conversation. 
2. Brand Building -- Creating your own “branded” hashtag can be a helpful way to promote your business and increase engagement. 
3. Helps your Audience find you -- Using hashtags is a great way to help people find your brand. Now, you can even follow specific hashtags on Instagram and LinkedIn. For example, if you use the popular hashtag #ecofriendly, you may gain some new followers and increase your engagement from people who follow this hashtag.

Hashtag Strategy

We recommend that you have a handful of hashtags that you use regularly and then a few other hashtags that are more specific to the video and relevant for current popular hashtag trends. Don't use a trendy/popular hashtag if you video is not related.

The recommended Quantity of Hashtags vary from network to network as do which hashtags are trendy or popular - so read up on the specific for each network and use the native hashtag tools for discovery:

• How to find Relevant Hashtags on Linkedin 
• How to find relevant Hashtags for a Business on Instagram 

Hashtags are not as powerful as they used to be since they dilute quickly because there is no quality control for relevance. Many people post unrelated content to what they think are popular hashtags regardless of relevance- algorithms exist to detect this based on the engagement (or lack thereof) of the first few viewers.  In other words - don't try to trick the system.

Hashtag Tools

Not only is it important to include hashtags in your posts, you also want to make sure that you are using them intelligently. It’s important to use hashtags that are popular and relevant to your brand. We recommend that you measure the popularity and performance of trending hashtags. There are many great tools available that help you find the best hashtags and also measure their trend over time. A few of these tools are: Hashtagify.me, Brand24, and Rite Tag. 

References:

Success in Your Social Media 

YouTube SEO Best Practices