"I would thank you from the bottom of my heart, but for you my heart has no bottom," is a good quote by an unknown author. "No duty is more urgent than that of returning thanks," by Saint Ambrose is a quote that will be suitable for any occasion. "Feeling gratitude and not expressing it is like wrapping a present and not giving it," by Dr. William Arthur Ward is one of the most popular quotes for expressing gratitude.
To write a thank you note, first decide who you are addressing it to, choose a card and a pen. Write a greeting, and make sure to spell the recipient's name correctly. After that, express your thanks with a general phrase, and add some details as to what you are thanking for. If it's a gift, write how you are going to use it, and how much you enjoy the gift.
After this section, it is a good idea to include a quote that is most appropriate for the situation. In the next part, write how you are looking forward to seeing that person again or talking to them again. In the end, restate your thanks using different phrases and adding more details. Sign the note and send it out quickly after the occasion.