Hydraulic leaks always have a source. The key is to look for a wet spot around a seal area or a hose area to find the source. If your tractor is dirty, tracking that down will be tougher. You might want to giver her a bath and focus on the front of the tractor around where the steering arm and the tie rods come together. Pressure wash if possible.
Once you get down to paint/metal, dry it off well and then start the tractor up and turn the wheel just enough to get a dribble. Then shut her down and get underneath, using an inspection mirror if you have one. Follow the tie rods from the wheels back to the chassis. Somewhere on the chassis you will find colored fluid (red, I believe). Be sure to wear glasses/safety glasses and DO NOT GET UNDER THERE while someone else moves the wheel. Hydraulic fluid can penetrate skin under pressure and will definitely bug your eyes in a fine mist. A small leak can turn into a big leak fast. Be careful. If you need to stand back ten feet while someone moves the wheel, that is fine.
Repeat the pressurization/leak/shutdown/inspection cycle until the source of the leak is identified.
Hope that helps.