Best approach to buying tools?

if you live near the country, find whatever paper/ shopper fsr, suctions sre listed in. farmers, die, move, sell out a farm, .... around here there will be a flat trailer or two full of boxes of tools.... box of wrenches, another full of sockets...... $ 5-6 a box.... 25 pounds o wrenches !
if you bid on bigger items, look them over good, and know what a new one costs. I have seen old stuff bring more than what it does new! if say,.. there is a hydraulic press, if you might want it, if you can, find the auctioneers helper, and ask what they generally sell for. he will know.... will be a range. or if he says they always sell stupid high, don't waste your time on it.
a farm estate sale will usually have a lot of good older brands. a high end farm will generally have quality tools.