Understand binary representation of integers and bitwise operators: AND (&), OR (|), XOR (^), NOT (~), left shift (<<), right shift (>>). These operate on individual bits of integers and are fast.
Practice converting between decimal and binary by hand. Know common patterns: n & (n-1) clears the lowest set bit, n & -n isolates the lowest set bit. XOR properties: n ^ n = 0 and n ^ 0 = n.