I feel your pain, there are a number of quests that involve a search, forest cover is perhaps the worst of these because the only thing that you can find is tracks. Here are the tips I can think of to help.
- Search from the center of the circle on the map, the location always seems to be the very center of the search circle.
- You can use your tracking skill in the zoomed out map, maybe try using it a few times on each square.
- Sometimes the tracks are mislabeled, you might find bull tracks if you're looking for a cow (how would they know?!).
Bear in mind there's no great penalty for failing a quest, you can sometimes go back to the NPC and tell them you give up. That might help you get another quest in a more timely manner, but I think I've had two quests active at a single time before.
I have somewhat of a love/hate relationship with the search quests but it always feels rewarding when I find what I've spent time looking for.