Here's one that came off the farm years ago and given to me by my grandfather in the 60's. To loosen rusted nuts and bolts, soak the parts with a 50/50 mixture of antifreeze and kerosene. It may take awhile, but believe me it does works. I still use it today on the tough ones.
Automatic tranny fluid and kerosine will work 10X better.
Rusted parts soaking in plain food grade vinegar will become clean metal after about a week and a light scrubbing with a wire brush.
cant ever use enough PB blaster or liquid wrench
antisieze anything you ever want to come apart again.
cringe on ordering anything from sears parts direct due to shipping costs and everything conveniently being $3.99 for a $0.05 part
if your taking apart complicated pieces or intricate things (especially things with springs and small washers screws/seals) take as many photos as you can. makes it MUCH easier to reference later on.
always look where your hand arm etc will end up IF that wrench slips, blades are sharp and just ran mowers have hot mufflers...