Laugh daily!
Make an effort to smile more and try smiling at strangers (without being creepy).
Spend time with playful people who make you laugh including pets and children.
Take yourself less seriously - share embarrassing moments and laugh at yourself. Remind yourself of a miserable person that you know so that you can avoid behaving like them (that really made me laugh for some reason!)
Try to find humour in bad or difficult situations rather than getting irritated or annoyed.
Build fun activities into your day such as watching comedies, going to a comedy club, reading comics, hosting a game night, reading funny books, telling jokes, karaoke, bowling, miniature golf, riding roller coasters and acting like a kid.
If smiling doesn't come naturally to you then practice laughing in front of the mirror until it does 
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