In addition to RickB's good advice, I'd like to add a couple of things about the hookup to the tractor.
1. The toplink should be adjusted so it is in the midrange of the float mechanism on the cutter. This is assuming you have a float device. It may be an elongated slot. If so, set the toplink length for the middle of the slot.
2. Each time before cutting, make sure the tailwheel is greased and all bolts on it are secure and it has a good pin to hold it in the pivot. Also check that all the bolts on its A-frame are tight and secure.
3. Check that your lower link pin are tight and that all the bolts on the mower's 3PH A-frame are tight and secure. Do not assume that the mower was assembled perfectly by the factory or dealer.
4. Check the gearbox for oil and that the bolts on it to the frame of the cutter are tight so the gearbox will not move.
5. Check that the slip clutch is adjusted properly if you have one. If you have shearpins, make sure you have a few spares and a hammer, punch, and adjustable wrench and pliers are a good thing to carry for changing shearpins.
6. Walk the area you are going to cut so you know where obstructions may be. If it's too big to walk or drive over, be very cautious the first time you cut it.
That's about it for what I can think of off the top of my head.