Binoculars, phone, water, compass, GPS with extra batteries, map if possible, and if required orange hat and vest. Sometimes I will carry a small stool in case I have a place I want to sit and watch for a while.
If possible bring a friend or family member to share the experience with. This second set of eyes is often invaluable in helping spot game while driving.
As a safety precaution when I leave the vehicle, I text a family member or friend about where I will be heading to when I take a walk about.
Luck favors the prepared mind.