At 3mths, night-feeds are not normally necessary. It's important to remember that all babies require additional fluids; this may be given as diluted fruit juice, preferably sugar free (see 'Dental Health' section). Growth rate tends to slow a little & this is the time to try mixed-feeding. Usually a {gluten} - free cereal is introduced.
This is mixed with some {artificial milk} & spoon-fed. Over the next 3mths, introduce different fruits (seedless, in a pureed form). Gradually increase the amount of solids until at 6mths, baby is usually taking 3 bottles of milk or 3 breast feeds/day & solids. Starting at 6-8 weeks is to be discouraged, since baby will become overweight, which may become a life-long problem.