What we read, listen to and think about shapes the way we view the world. If we can find simple things to be thankful for everyday we find happiness.
It's paradoxical, but we do not find happiness by trying to make ourselves happy - but rather by thinking less about ourselves and more about people less fortunate, we find peace, satisfaction and more joy. Doing something good for another person often has more benefit for the doer than the receiver.
I think it's a good idea to become involved in volunteer activities, or take individual acts, that help other people - for a very selfish reason - it makes us happier. There's really nothing wrong with being selfish if it leads to you being happy and has an added benefit of aiding others.
I also think it's a good idea to become involved with some sort of spiritual activity - whether it be a church or just finding devotionals or thought of day material that have positive messages.
We start by looking inward and as we grow we become more outward focused and realize that doing simple things to take care of ourselves allows us to do more for others. Taking a news-break, reading and listening to positive messages, buying fresh flowers, eating healthy foods, exercise, breathing and meditation - can all help us, so we can help others.
Rejoice in the Lord always; again I will say, Rejoice. Let your gentleness be known to everyone. The Lord is near. Do not worry about anything, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus. Finally, beloved, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is pleasing, whatever is commendable, if there is any excellence and if there is anything worthy of praise, think about these things. Keep on doing the things that you have learned and received and heard and seen in me, and the God of peace will be with you.
-Philippians 4:4-9 (NRSV)