Once your estimate is approved and you start working with a client, figure out who your go-to resources are within your client's organization.
Who is the person to help you remember names and who does what?
Who is the person that can help you with the copy machine?
Who can help you book a room for your next meeting?
For me, with marketing related projects, I often seek-out the person or team that manages the web site because I know I will likely need their support with my work.
Hear tip #5 here:
What job function or roles are your go-to resources when working with a client?