What is the best way to clean an infant (1~12 month)? What I do now is take off her clothes first, then dip into a baby tub filled with warm water.

Bath time can be fun. You can put her in a partially reclining baby tub or other baby bath device (some even come with safety belts!), and using a baby or sensitive skin cleanser and a washcloth, bathe her all over, then rinse all over. Babies do fine with only a few baths each week. Make bath time fun by talking or singing to her entertaining her with bath toys.
Sponging. No need to give tub baths everyday.You can sponge them down with a wash cloth with warm water.Still pat dry.Be sure you are away from any air vent.Tub baths once or twice a week should do unless your child is messy with poop, vomits or pee.