Every child is different, but here is some great info from: http://www.ucsfchildrenshospital.org/education/baby_bottl...
When is my child ready to be weaned from the bottle?
In general, children can try a cup at 6 months and be weaned off the bottle around 12 to 18 months. Children are ready to be weaned when they:
* Can sit up by themselves
* Can eat from a spoon
* Show more interest in solid foods
* Have an established routine for mealtimes
How do I wean my child off the bottle?
* Wean your child during a relatively stress-free time. It is not a good idea to start when a new sibling has just arrived or when the family is moving to a new house.
* Introduce the cup early, at age 3 to 6 months. Let your child hold and become used to the cup without liquid.
* At age 8 to 10 months, substitute a sippy cup for a bottle at one feeding during the day. Choose a feeding when your child usually drinks just a little, rather than a major mealtime. Use this same feeding time to use the cup every day for a week.
* Every week, introduce the cup at another feeding, slowly decreasing the number of bottles your child receives.
* Feed very slowly. Help your child hold the cup and tip a small amount of liquid into his or her mouth.
* Some children may need to suck as a way for them to control their behavior. This sets their mood to accomplish certain tasks such as sleeping, concentrating and running. Some children may continue to suck on a pacifier or bottles of plain water for the first few years.
* Consistency is key to successful weaning. Be sure to give your child the cup at the designated feeding time and don't switch back to the bottle at this feeding.
What can I put in a bottle and what can I put in a cup?
* Put only breast milk, formula or water — no cows' milk before 12 months — in a bottle. Never put juice or other fruit-flavored drinks in a bottle.
* During the weaning process, only use water or milk in the cup. (Remember, no cows' milk before your child is 12 months old.) If you put juice in the cup, your child may come to expect it. After weaning you can offer diluted juice in the cup.
How can I make weaning easier on my baby?
* Offer other comforts such as a soft blanket or stuffed animal, or play soothing music.
* Spend extra time cuddling with your child during the weaning process.
* Buy cups with handles, spouted lids or baby cups with straws to make drinking easier.
* Be a positive role model and drink from a cup with your child.
Good luck!