4WD makes a front end loader about 20 times more useful. ALWAYS keep the bucket low to the ground when loaded. Raise/lower it slowly when loaded, especially while moving. The first time you get the tractor rocking, you will understand why.
If 4WD, load all four tires with calcium chloride solution. If I were loading tires on a tractor for the first time, I think I would pay extra to be sure they had tubes in them, on the assumption that the rims would last longer this way. I will be getting a new set of rear rims on a couple of loaded tire tractors without tubes some ("Surprise!") time in the future and am not looking forward to it.
Grease all tractor and implement fittings for every major use occurrence. In the Summer I grease everything once per hayfield; since I started this, I have not had to rebuild any shafts with universal joints (a pain to fix and dangerous when they break in use).
NO RIDERS WHEN YOU ARE WORKING! You don't need to concentrate on a rider when you are bush hogging, plowing, etc. - you need to concentrate on the job at hand.
If you will be mowing rough, unimproved fields, strongly consider a mower (bush hog) with a "stump jumper". This is a big, round-bottomed center hub that the blades attach to. When you drive over a stump/big rock while mowing, the blades will flod out of the way and then the stump jumper lifts the mower up over the obstruction. You and the tractor get all shaken up (Fish Wife missed an earthquake while bush hogging once because she thought she had just mowed over a stump), but the obstacle DOES NOT stop everything abruptly (and break something).
If you have a gravel driveway, and box blade with ripper teeth is wonderful for maintenance. You can tear up and smooth the hole surface down for a few inches, eliminating potholes, washouts, and other problems. Since we got a box blade, our need to get new gravel has dropped to about 1/3 what is was before - we just re-dress the gravel a couple of times a year instead. Box blades are also great for fields, new lawns, riding arenas, and presumably ball fields and other places.
When something goes wrong in use, stop everything, lock the brakes, and wait for all parts to stop moving before investigating and attempting corrections. Don't let the tractor have a chance to roll over you, don't let attachments have a chance to grab you. Moving PTO shafts are extremely dangerous, especially if you have any loose clothing.
Wear long pants and boots while bush hogging. Your legs and ankles will thank you when a rock or a heavy stick is thrown forward into them by the mower. (It actually feels like pain rather than thanks, but they won't bleed or break nearly as often with protective clothing rather than bare skin receiving the impact.)
Hearing protectors!