If you've just applied for a hundred copy editor freelance jobs--do you have to write a thank you note to each and every one of them? While it may seem incredibly time-consuming, the answer is a simple one--yes.
Writing a thank you note is considered the professional thing to do when it comes to job interviews. In some cases a simple e-mail thank you may suffice, but it is always nice to drop a hand-written note in the mail as well. You don't have to write endlessly, but be sure to personalize the note and include your full name and contact information. Keep the card or stationary simple and professional, and avoid any outlandish stamps or loud envelopes.
Make sure that you get the thank you out as soon as possible after the interview. Sending a belated thank you is nearly as bad as forgetting completely. If you are not sure what to write just keep it simple and short. It is also a good idea to express your interest in the position you interviewed for before closing. If you think of the thank you note as part of the interview process, you will be more likely to remember to send one--and more likely to get the job.
You may also want to consider sending thank you notes to anyone who has helped you set up an interview or given you information that leads to a job. It's a nice touch and people like to feel appreciated.