step by step
1. Incrementally; in the proper sequential order. Make sure you follow the instructions step by step—don't skip around or it won't turn out right.
2. Slowly, carefully, and deliberately; without being careless or in a rush. It is entirely possible for this project to succeed, we just need to proceed step by step. Major life changes like this can fluster anyone, so just take everything step by step.
step-by-step
1. Lit. [walking] one step at a time. The old man slowly moved across the lawn step-by-step.
2. Fig. little by little. Just follow the instructions step-by-step, and everything will be fine.