After you find work, contact every single person who helped you in any way to let them know you found work, and thank them for helping you.
Also let them know that you hope you can help them in the future.
While expressing thanks is always polite, in the future it will also help both you and the person who helped you since it strengthens both of your networks. Here's an example note you can send to each of the people who have helped you find work:
The more the person helped you, the more personalized the message should be. Everyone who helped you in any way will appreciate at least a short thank you note.