get yourself a shop/service manual for the tractor. it will give details to trouble shoot along with exploded diagrams and how to tear it apart, check stuff and put it back together.
most tractor manufactures you can find "online part manuals" for free online, that give very basic diagrams just enough to double check part, and get a part number
owners / operators manual. = check fluids, how to use machine, general safety warnings, were grease zerks are, when to do oil changes and like.
with new to you, used tractor, filter check (oil, air, hydraulic oil, fuel) and see if they need replaced. (air filter there is a chance it has a inner and outer air filter)
check the battery, and its terminals and cables for any corrosion / chunks of insulation missing.
see about draining old fuel and putting new in. ((careful diesel units and/or even gas you may need to prime the fuel and fuel going were it suppose to))
check general wiring. good chance it been ripped out / broken off / cut / damaged *been there done that* in fixing.
there might be chance instead of glow plug, there is a "ether" or some such maybe for a cold start kit installed. and ether needs to be added.
if not already get yourself a larger 110v battery jumper / charger. those little car/truck jumpers not enough power.
check your water level of the batteries.
find your radiator, hydraulic oil cooler (looks like a smaller version of radiator), and transmission oil cooler (another small radiator) make sure it is not full of gunk / dust / weeds / mud.
make sure you got your hydrualic lines all straighten out and not trying to raise FEL or curl the bucket, or something on rear in with the 3pt. when trying to start unit.
double check any wiring harness connections. (larger plugs with a bunch of wires) they can come loose and corroded.
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most above is general yada yada. but you might find something.
