Pro-Tips: Tractor Safety #263 / Smarter Not Harder #833
On the list of shite I wish I'd been reminded of before having my pucker factor achieve 'frequent flyer status,' this would top the list:
How to decrease your chances of rolling a tractor you are strapped to whilst using ground engaging implements (plows, tillers etc..) on a slope: Keep your UPHILL tire in the furrow of your last pass.
A tractor will flip when the center of gravity (COG) of the uphill rear tire breaks the vertical plane created by the downhill rear tire's COG and the COG created by the two front tires (usually at the mid point between the two front wheels). This can be mitigated by keeping your uphill rear tire as close to level as possible and going SLOW (since you're using ground engaging equipment you should be in low gear anyways). What you're looking out for as you're going slow is an instance where there is dip in the path of your downhill tires and a bump in the path of your uphill tires, this is where you get close to exceeding the 'tip angle' of your particular tractor (they make gauges for this that indicate your 'tip angle' but your sense of self-preservation is apparently just as accurate as those gauges).
Here's a great resource for tractor safety tips -- best I've found so far. If you have one you like better please drop a comment cuz I'm all about not dying on, or because of, a tractor.