Gratitude is one of the 24 character strengths. It has its own holida in the US and Canada. It has a host of positive health benefits. 

Consider Louie Schwartzberg gorgeous 6 minute film on gratitude.

Here are some nice guided meditations and exercises to focus you on gratitude:

• Jack Cornfield offers a very soulful written guide on Gratitude and joy. 
• Relax for a while has a nice youtube version. 
• Still Mind offers two easy to implement exercises. 
• Deepk Chopra has an 8 minute guided meditation on his website
• Agapi Stassinopoulos, author of Unbinding the Heart: A Dose of Greek Wisdom, Generosity, and Unconditional Love and sister of Arina Huffington, provides another guided journey with a lovely video. 
• Keep a Gratitude Journal. This can be physical journal or an online one or an app. 
  • Physical: If you want a bit more structure than a blank book try the Five Minute Journal. It has you respond to questions twice a day.  Another Five Minute Journal is substantially less expensive. 
  • Oneline: Gratefulness.org is an interesting site offering online journaling and interaction. Greater Good has a free thnks4.
  • Apps: Gratitude is a beutiful IOS app. Here is a list of 5. 
• Tiny Buddha offers 11 tips for a more powerful gratitude Journal as does the Greater Good Society.