pedal/cleat compatibility question

I have purchased a pair of Shimano PD-1056 pedals, used, with no cleats. Its my understanding that these are LOOK compatible, but use older, non-keo clips.
My question is, what am I looking for? I see a lot of "delta" style clips on ebay, plus many other "look" compatible. I'm kinda worried that the keo style may have become the "norm" and not mentioned in the ads.
so whats what, or am I barking up the wrong tree, or what?