There's nothing like a fresh-out-of-the-bath baby, so it can be tempting to pop him in the tub every night. But babies don't actually get very dirty (just wait for the toddler years!). If you're careful to clean your baby thoroughly at each diaper change, you probably won't need to bathe him often perhaps two or three times a week. The bath doesn't have to be lengthy, either, just long enough to wipe off any debris and peeling skin that's collected.
It is true that once your baby starts crawling, you may find that he needs to be bathed more often. Just keep in mind that overly long baths may dry out his skin. To prevent this, keep bath time short (5 to 10 minutes), and apply a moisturizer to his skin after every dip. And don't let him sit for long in soapy water play first, then soap up, rinse, and towel down.
Get tips on keeping your baby's skin moisturized.
FYI: Keep it simple: The best baby soaps are free of both fragrance and deodorant. Baby washes have some antibacterial properties, but don't overuse them like regular soaps, they leave a residue on your baby's skin if they're not rinsed off completely.