Have neither played nor spoken about cracktop in over thirty years, but if memory serves…
Play commences with each player throwing (spinning) his top at the same time. First guy whose top stops spinning is ‘it’. His top sits on its side as the target. In turns, the other players throw their tops (with a fearsome and perhaps sadistic intent) in an attempt to score a direct hit.* If you had a direct hit, your turn was over and you were saved the indignity of replacing the guy who was ‘it.’ If you missed, you advanced to a secondary stage of silliness which incorporated endless opportunities for arguments, disputes, and general verbal fencing: you had to bring your top into contact with the target top before your top stopped spinning — preferred and most reliable method was to hold your string taut, straddle the spinning top, and drag it into contact with the target by pulling the string along the spinning point. (Many of the low guys in the pecking order would be exposed for a kick in the pants while performing this ungraceful maneuver). A far more accomplished and enviable technique (but naturally more difficult and risky) was to scoop your spinning top onto your palm, carrying it (it must continue to spin all the while) to a point above the target, and dropping it onto the target. The clumsy guys would become ridiculous when attempting this one, and could easily be goaded into trying something which would assure them a turn as target. The game was everything a good street game should be: skill was evident, the uninitiated were pitiful, and there was a thinly veiled aroma of violence about the whole affair (anyone remember absurd “knucks” sessions with playing cards?)

*footnote from above: hilariously unlikely folklore of some kid on another block or another neighborhood or another planet shattering a top into flying splinters. We would spend more time relating and believing such crap than actually playing the game!