Look for tracks, droppings, dusting sites, strut marks, scratching and maybe, if you are lucky, a few dropped feathers.
Of all the signs turkeys leave, tracks are found must often. Turkeys walk just about everywhere, so they leave tracks in the sand, soft dirt, snow, mud, and even defrosting ground. Tracks are not always obvious. Complete and partial tracks, such as the imprint of a toe, are easy to miss.
Start taking scouting very seriously a week or two before the spring season opens. That's usually when winter flocks break up, and fresh tracks found a few days prior to hunting season can hold promise that the turkeys will still be in the particular area when it really counts.
Tracks are one of the few sure things in turkey hunting. They are irrefutable evidence there are turkeys in the area. Tracks give you a place to start, it's your job to put yourself in the right place from there on.