Dawn your best camo, grab a weeks worth of rations, a flashlight, and a camera. Take a week off of work, find a group of bushes and sit in the middle of the biggest bush you can find for several days. Switch bushes periodically to be sure you have covered all of your property. Stay all week long, if you see any hogs, take their picture, if not, you dont have any hogs...

This is completely sarcastic of course.. Best I can say, is place a pile of corn or hog finisher out somewhere where you can easily check for fresh tracks. See what happens...