You didn't receive anything monetary, or any sort of gift, and you didn't have a large event to warrant a Thank You note, so why would you send one out? Well, someone gave you your time, and you should let them know that you appreciate them taking the time to speak to you, but when do you write one? How do you write a professional one? Would an email suffice? Here are all of your answers...
When To write a thank you note
While it really is up to you whether you think it would be appropriate to send a thank you email or note, here are some instances where you may want to write one:
Overall, whether you write a thank you note or not is somewhat dependant on the relationship you want to maintain with the other party. They keep your name in the other person's head, and they are more likely to remember who you are if you should get in contact with them again.
Letter vs email
You've now decided that it is worth it to send a thank you to someone who took the time to do something for you, whether it be a task or taking the time to meet with you. However, what is better: an email, or a hand-written note?