1. One thing at a time
   - in small stages, piecemeal, step-by-step, stepwise

1. A little bit at a time
   - piecemeal, little by little, in stages 
2. In a gradual manner
   - gradually, step by step

See also: gradual

• Demeter
• Demetrius
• Demetrius I
• Demetrius Poliorcetes
• demi-
• demi-glaze
• demiglace
• demigod
• demigoddess
• demijohn
• demilitarisation
• demilitarise
• demilitarised zone
• demilitarization
• demilitarize
• demilitarized zone
• DeMille
• demimondaine
• demimonde
• demineralisation
• demineralise
• demineralization
• demineralize
• demise
• demisemiquaver