I usually just do a general search for the position I want (sometimes even the player type if I want a specific one). Then, I put "NHL" and "Gold" filters on it just to help reduce the crap I don't want to see. Then, I search and just look through the auctions until I see a player that looks appealing.
Then, I go back to search and add his team/player type to my filter so I'll mostly only see auctions for that guy. Sometimes, I'll even put a "buy now" maximum filter on if I see a decent price to make sure I know what the lowest available price is.
I have missed out on a few guys by being this thorough though. I saw an Eric Staal for like 3,950 yesterday, but by the time I went back to buy him, he was gone. I did score Vlasic for only 1,700 coins though. Once you start to get a sense for what players are worth, obviously, you figure out when to jump on them. This would also be a good way to flip players for profit. But like Alan mentioned, timing has a lot to do with it too.
For example, I was on an hour ago and grabbed a 15 game duration card for a 1,400 coin Buy Now. No idea why the guy priced it that low (I guess maybe he wanted insta-coins...but he probably could have gotten at least 800-1,000 more just as quickly), but I'm not complaining.