Some things that work for me, at least in terms of commerce:
Beat the bushes. I hit every antique show, flea market, yard sale and estate sale I can find. I don't always find stuff but sometimes I do.
Broaden your reach. Maybe you study up on nonsports and try to make money there.
Obscurity means lack of price transparency. I look for categories of items where pricing is not easily understood.
Price discipline is paramount when purchasing. It is a numbers game. I have a price and that's it. If the seller says no, I walk (or at least I should; still licking my wounds over a bad deal at the show in August).
Follow Mr. Keeler's advice (thread needs a card anyway)
I hit 'em where
they ain't. If there is a surge in excitement over Mantle, buy Aaron. If T206 has an extreme year, buy T205.
In the collecting arena, I used to just grab whatever caught my eye. Now, what works best for me is to try and go after only very specific cards for specific reasons. Like, I wanted to complete my E254 Tinker-Evers-Chance, so I went after a Chance in LOTG. I went to the National looking to upgrade some specific cards.