You can offer a sippy whenever you want, some babies take to them early (like 5-6 mos) and others never do. My son wasn't really into sippies until after a year. He did like drinking out of water bottles and regular glasses.
You should take out the no-spill valve (if your cup has one) when they are first learning to use one.
You should take out the no-spill valve (if your cup has one) when they are first learning to use one.