The most common triggers for mood swings are:
Stress from major life events, both positive and negative
Lack of sleep
Erratic schedules
Caffeine and alcohol
Certain medications, such as antidepressants and corticosteroids
Seasonal changes (for example, winter can worsen depression, while summer can increase the risk of mania)
Stopping bipolar meds or varying the treatment schedule
Thyroid problems
Substance abuse
Mood Swings: Coping Strategies
Control stress
Keep a regular schedule
Practice healthy sleep habits
Get moving
Avoid caffeine, alcohol, and drugs
Write it down
Tracking moods
Exercise
Nutrition
Avoid overgeneralizing negative outcomes
Make space for the gray areas of life
Learn to laugh at yourself
Reflect on your situation objectively
Know when to walk away
Take a five minute break
Talk to a friend about it
Find a calming routine
Think before you speak
Eat something
Go for a walk
Reduce your stress
Spend time with your friends and family
Maintain a well-balanced diet
Incorporate herbs, vitamins and supplements into your daily regimen
Know that the causes of mood swings can vary
Understand the psychological and social conditions that can contribute to mood swings
Source:
http://www.wikihow.com/Control-Mood-Swings
http://www.goodtherapy.org/learn-about-therapy/issues/mood-swings
http://www.everydayhealth.com/bipolar-disorder/bipolar-disorder-mood-swings.aspx