At 9 or 10 months, I transitioned A from a regular bottle to a trainer sippy cup.  It looks like a bottle, and has a flexible spout instead of a nipple.  Once I saw he could drink out of it, I threw away all bottles.

He used this for a couple of months instead of the bottle and it worked great.  Then, we started practicing with a straw cup (I really wanted him to drink out of a straw – better for their teeth, and way easier since there are straws at restaurants and such).  It took quite a few cups to find the right one, and I showed him a lot how to suck through the straw, but once he got the hang of it we threw away the trainer sippy cups.  I used a separate cup for water (not sure why?) and I absolutely love these.
Next up will be drinking from a regular old cup 🙂