H.R.
You should start any time now. My daughter was about 9 months or so when we started. She never (and still doesn't) liked the ones we started with...the Avent Magic Cups. I finally realized that she would drink from a straw (she'd been doing that since about 6 months) so I bought some Munchkin straw sippy cups and those are all she'll drink from by herself. She still won't tip up a regular sippy cup by herself, but I know she'll learn to tip it up eventually.