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

• genus Actinomeris
• genus Actinomyces
• genus Actitis
• genus Adalia
• genus Adansonia
• genus Addax
• genus Adelges
• genus Adenanthera
• genus Adenium
• genus Adenota
• genus Adiantum
• genus Adlumia
• genus Adonis
• genus Aedes
• genus Aegiceras
• genus Aegilops
• genus Aegypius
• genus Aegyptopithecus
• genus Aeonium
• genus Aepyceros
• genus Aepyornis
• genus Aerides
• genus Aerobacter
• genus Aeschynanthus
• genus Aesculus