Your question is very good and important, as most design or process engineers 'forget' to ask it, and it often comes up too late to be caretaken at the correct stage of the process. Wrong type of actuators and actuators could be selected, and chances for integrated signal systems bypassed as to late to incorporate.
A control valve might also incorporate a complete control station including a couple of flowmeters and isolation and check valves in addition to one or several controlvalves and safety valves, all can and might have several signals. The question might also be reversed: what signals do you want and need, and in whitch form and current.
You could also try to be a bit more specific and post again in the valves forum.
