What is the best way to wean my baby off of bottles?

Depends on the age. If a baby is old enough to sip from a cup, he can drink his milk or water from a regular cup (with help) or from a sippy cup that has a lid. At this age (usually 20-24 months), the parent can have one talk with the child about the bottles going "bye-bye", and make all the bottles in the home disappear overnight. The important thing is to judge when the baby is truly able to drink from a cup.
Less Available. Make baby's bottles less available. Gradually, cut back the number of bottles offered during the day. Use a sippy or other cup, instead. Sippy cups can be introduced as early as 6 months. Try to get baby completely off the bottle by 12-15 months of age.
Try the sippy early. Try introducing the sippy cup early- around 9 months for most babies. Some babies may be able to manage taking a sippy cup even earlier than that. Early introduction of the sippy cup rather than waiting too long may help your baby transition easier to the next step. Don't get too frustrated early on if she doesn't take to it immediately; try again over and over until she gets the hang of it.