If congratulations are backed by a gift, as soon as the donor will agree and will give you a gift, just say, "Thank you." In some cases, you can attach the donor's name.
Open gift. Say "thank you" again, even if the gift you don't really need or don't like. If the donor is your best friend, kiss him on the cheek.
If speech does not imply the delivery of a gift, but requires a longer, detailed answer than in the first case, listen to the speaker. Then take the word. Start the speech with the words "thank you", "thank you" or other synonyms. Describe the speaker to the audience: tell us about the positive qualities which he has shown in your presence, about the interesting situations when the person helped you is unusual or unexpected way.
Express gratitude to the man for his location. Note how happy you are to meet him. Finish the speech with the same words that began: "thank you."