The newly diagnosed patients has a lot of stuff to deal with. Providing peripheral help is great, but please to badger the patient repeatedly asking how you can help. Then it becomes just one more thing he/she has to deal with. Another key point is that the cancer patient needs support, but not someone forcibly trying to take over. There is already so much that you can't control when you have cancer. Well meaning friends and family who try to do more for the patient than they need to have done, are taking away what little control the patient has left.
Another thing that tends to be a common occurrence is that friends and family go overboard trying to do everything for the patient in the beginning and end up getting burned out. The result is that after hovering over the patient's every move for a while, they start to draw back because they have their own lives, family, responsibilities, etc. to get back to. After the initial coddling, this often makes the patient feel abandoned when their supporters draw back.
So what I would recommend to friends and families of cancer patients is to support the patient to the extent that think they will be able to continue that support indefinitely. And don't try to do more than you can sustain or more than the patient needs. It is equally important for the patient to feel supported and to know the limits of your support, as well as not having to deal with somebody trying to take control away from them.
If anybody has additional thoughts and advice based on their experiences, please post them here. I think your input would be helpful to many.