Here are some experiences I've (hopefully) learned lifetime lessons from and a few I (thankfully) haven't:
Never forget what you're dealing with. If that wedge can cut through a block of wood, it can cut your fingers off.
Once the ram contacts the round, remove your hand. Don't think that holding the round while it's being split will make any difference. It won't.
A retracting ram can pinch fingers and hands. Avoid reaching in until the ram has fully retracted.
If the round doesn't completely split or pinches on the wedge, resist the temptation to lift it off the wedge by hand. I got a finger seriously pinched doing this. Only did it once. To free a round that's stuck on the wedge, hook a length of chain around the round and extended ram, run cylinder in reverse.
Stand away from the round while splitting. Yup, a tough one can suddenly fly apart and do some serious injury. Also, a heavy split landing on your foot won't make for a good day.
Knots, crotch wood, burls etc. can and will do unexpected things when they break. Make sure your body parts are clear when splitting those things.