It's funny what you take for granted. I recently became painfully aware of how important communication can be. I tend to have a very low key style of doing things. I basically do things but don't generally feel the need to make a big deal of things. It became a big deal. Now I understand that even though I know I do, it doesn't mean people know I am doing.
So for me I have learned the power of a "cc:" on my emails and just a quick email in general. When you are working with clients and in particular prospects, make sure you let them know you are working for them or on their stuff. Jot them a quick note or copy them in your correspondence. I believe this simple item can go a long way into building a strong bond with who ever is important in your world.