my car has a little puddle of transmission fluid every morning, the car runs fine as long as I keep adding fluid. what do I need to do and what will it cost?
Have someone go under the vehicle and make sure none of the transmission pan bolts are loose.
The only thing you can do is look at it or have it looked it. There are a number of different places it can leak from (including the pan as Tester noted). Since there are a lot of different places it might leak from you just need to find the leak.
Best case is a leaky pan or leaky cooler lines. Somewhat worse is leaky axle seals. Worst case is a bad front seal since the transmission has to come out for that. But there’s no way to say without someone getting underneath and looking for it.