In your prayers, before you ask for blessings, pour out your heart to God in thanks for the blessings you have already received. Thank Him for your family, for friends, and loved ones, for leaders and teachers, for the gospel, and for His Son, Jesus Christ.
You can also express gratitude to the Lord by the way you live. When you keep His commandments and serve others, you show that you love Him and are grateful to Him. Express appreciation to everyone who helps you in any way.