No such thing as too much communication!!
As with any relationship communication is key. I have found it is far better to over communicate than under communicate. Clients appreciate knowing what is going on and one of the biggest complaints about recruiting is lack of communication. One of the biggest ways to do this is to manage your inbox. Do not let it become overwhelming and a place where emails go to die. Stay on top of it. Respond to emails form your client in a timely fashion. Create rules and alerts to help deal with some of the emails and when in doubt communicate to your client about everything. Trust me they will appreciate.