BitTorrent currently contributes a significant amount of inter-ISP traffic. This has motivated research and development to explore caching and locality-aware neighbor selection mechanisms for costly traffic reduction. Recent researches have analyzed the possible effects of caching BitTorrent traffic and have provided preliminary results on its cacheability. However, little is known about the specifics of caching design that affect cache effectiveness and operation, such as replacement policy and cache size. This study addresses this gap with a comprehensive analysis of BitTorrent caching based on traces of user behavior in four popular BitTorrent sites. Our trace-driven simulation results show differences in BitTorrent traffic caching compared to that of the Web and other peer-to-peer applications. Differently from Web and other peer-to-peer caching, larger caches are necessary to achieve similar caching effectiveness in BitTorrent traffic. Furthermore, in BitTorrent caching, the LRU replacement policy that takes the temporal locality into account shows the best performance. We also use a locality-aware neighbor selection mechanism as a baseline to evaluate the LRU caching effectiveness. We find that LRU caching can provide greater traffic reduction than locality-aware neighbor selection in several scenarios of cache size and number of ISP clients.