There are a couple of options for guestimating the wind direction when no obvious clues exist.
The best one is the GPS - For an approximate idea just fly to your destination and compare Ground and Air speed. Complete a high circuit around the target comparing GS and AS and it becomes obvious where its coming from.
Even if you only use it to get a rough idea as you get closer to the ground the movement of the trees etc gets more obvious and you make minor corrections.
If you want to be more accurate use the "wind aloft" feature. Both my Garmin GPS's have it so I assume it's standard on other aviation GPS's. Its easy to use.
The second is the manual version. Fly a square circuit at a fixed airspeed straight and level. Pick a "time unit" for each leg and fly it precisely (say 1 minute per leg but with upwind and approach being each a half of the unit time.) Do tightish turns on accurate compass headings.
If you are in nil wind you would fly a square with the target in the midpoint of the approach/upwind leg. That is after you've flown the square you should be directly overhead the target.
If there is wind you will end up downwind of the target. Turn toward the target and you are into wind.