Some tips for using hashtags are to be specific and concise, limit the amount of hashtags in each post, and cater the hashtags to each social network appropriately. Hashtags should be used to generate a natural buzz around a topic, so refrain from including obvious branding when possible.
Join an existing conversation by using hashtags already in circulation. This helps to attract new followers and fans and gives existing followers a feeling of acknowledgement. More hashtags per post doesn't necessarily mean more exposure. Posts flooded with hashtags often come across as spam or overly marketed, which can lead to readers ignoring them.