In [1], Arıkan introduced polar codes and proved that they are capacity achieving over symmetric binary memoryless channels under successive cancellation decoding (SCD). However, the metric used in the SCD algorithm does not incorporate knowledge of future frozen bits. In this paper we take a fresh look at the SCD algorithm and propose two decoding algorithms a) successive cancellation with back-tracking (SC-BT) and successive cancellation with look ahead (SC-LA). Both algorithms try to improve the performance using a memory of size O(N). We also extend the SC-LA algorithm to work with successive cancellation list decoding (SCLD).