A professional thank you note should have a handwritten touch and include a greeting, a specific statement of thanks, a mention of the impact of the event, a kind closing and your signature with an appropriate sign-off. When writing the greeting, be sure to address the individual by name.
In the statement of thanks, point to certain aspects of the event that stood out. Make it personally relevant by adding a detail about how you feel affected by the event. In closing, you can include an offer for a follow-up or professional get-together, if appropriate. Personal or decorative stationary can add a nice touch to any gesture of thanks and demonstrates that you put care and forethought into expressing your sentiment.