Giving gifts is a powerful way to express gratitude. When you give someone a gift, think about what this person would actually appreciate. What does this person need? What would this person like to have even if he doesn't actually feel a need for it now?
When you see an item that you feel would be great to give someone as a gift, ask yourself, "Who am I grateful to that would appreciate this as a gift?"
Books are great gratitude gifts. A book can be read over and over again. And even when it is read only once, the book on the bookshelf is a frequently reminder that you are grateful.
There are many inexpensive items that would be greatly appreciated as a "Thank you" gift.
If you want to make sure that what you will be buying someone as a gift is something that this person would truly appreciate receiving, think of someone you can consult. You might ask someone to ask for you, "Is there something that you probably would not buy for yourself but would appreciate someone buying for you as a gift?"
A general rule to keep in mind is, "Don't just get someone a gift that you personally would like to receive. Give what you think this individual would like."
I once met someone who is considered an expert gift giver. "How did you develop your expertise?" I heard someone ask this person.
"I keep asking people, ‘What are the gifts that you have appreciated the most?' I even ask this to strangers I meet in lines at stores. I have heard a tremendous amount of people answer this question. This has given me a strong sense of what different people appreciate as gifts."
(From Rabbi Zelig Pliskin's book: THANK YOU! Gratitude: Formulas, Stories, and Insights: Artscroll Publishers)