Terk actually has one product that works, and it is their passive AM antenna. I do not remember the model, but I am sure it is on their ever-stylish web site; you can also find a link to it on the web site of that beloved southern California talk show icon, Mr. KABC, at
www.mrkabc.com (he also recommends ccrane stuff for the serious AMer).
I have one of these antennas. You don't even have to connect it! Place it near the receiver (not in a metal rack, thank you), tune to the station you want, then tune the antenna and orient it till the station is the most clear. This antenna is directional, which is one of the reasons it works so well, but that means that you have to move it for each station. But didn't you say "best" ?
Second would be the "long wire antenna" (see google), which is what Larry was describing. Simply put, the longer the better, and a ground helps immensely.