(1) Read whatever you can on "classic" audio gear. C. Kittleson's "Vintage Hi-Fi Spotter's Guide" (Volumes 1 & 2) are good places to start. (2) Learn as much as you can about older tube or solid atate gear and about "cult" pieces (tube or solid state) that bring good prices even though they aren't particularly noteworthy as hi fi. I got a McIntosh C-11 preamp, MR65B tuner, and MC-240 power amp for $50 each at an estate sale. When I asked the guy if he had any stereo gear he said "just some old junk in the garage". All 3 pieces worked perfectly, I sold them later for $2300. I found an AR turntable for $5.00 at a flea market which I later sold for $95. (3) Have a good wad of cash with you. 'Nothing worse than losing out on a great piece because you don't have the cash and they won't take your personal check during a moving sale. (Would you take a stranger's personal check if you were moving the next day?) The most important thing is to educate yourself. Know what you would like to find BEFORE you go out looking... and (4) make sure you know the model numbers that are desireable and the one's that are not; not EVERYTHING McIntosh (or anybody else) made is desireable. (The Scott 310-E tuner is the highly prized one, not the 310-C). "Infinity" and other companies changed hands so often that there are periods when really good stuff was produced and absolute junk, depending upon who owned the company at the time. When Arnie Nudell was an owner, Infinity was pressing the edge of speaker technology, not so when TWA Airlines owned Infinity. You've got to learn this stuff the way an antique dealer learns his/her craft so you know instantly if you buy it or don't. (5) Expect to get "burned" occasionally with a "bum" purchase, we've all done it. But the more knowledgeable you become, the less this will happen. There is no substitute for knowledge. I bought old rusted, dirty, homemade and kit tube amps for $50, and the guy laughed at me to his wife that some jerk would actually give him $50 for all this rusted junk. I pulled all the tubes, among which were four Westinghouse 300B's, and told him to throw the amps in his scrap heap. My Cary SEI never sounded so good when I replaced the Sovtek 300B's with the Westinghouse. (New Westinghouse 300B tubes have a "retail" of about $1000 a pair). I got a bundle of smooth plate Telefunken "diamond" 12AX7 tubes by buying old, dented Dyna preamps ($10 to $15) that I guessed probably still had the original, stock Telefunken tubes that lasted forever in that simple circuit (Note: the tubes are marked "Dyna" but I knew from the plates and the "diamond" on the bottom that they were genuine Telefunken's.) Know what to look for... and why you would buy a certain piece of gear.