Also, if you haven't thought that far ahead, check your local Home Depot for wall-plates to accommodate AC and HDMI connections. That is a huge plus for WAf.
It is easiest to install these when you are installing the TV mount so neither gets in the way of the other.
I installed female HDMI plates, but think I would just go with a setup like this if I did it again. HDMI cables do not always snap fit and I worry that the in-wall HDMI cable might come loose from the wall plate. With the bulk cable port as below, all of the connections are out in the open.
This one is recessed for flush mounting the TV which you probably don't need.