There are several synonyms for the phrase "a little at a time." One of the most common alternatives is "bit by bit," which means progressing in small increments. "Gradually" is another synonym that means slowly but steadily. "Step by step" means to proceed one step at a time. "Piece by piece" implies doing something in small fragments. "Incrementally" refers to taking small steps to make gradual progress. "By degrees" suggests progressing gradually or slowly but surely. In summary, these synonyms all convey the idea of proceeding carefully and incrementally, rather than all at once.