I recently posted a video of my son happily drinking from a sippy cup all on his own at ten months. A few friends of mine are having difficulty getting their children to do the same even though their children are much older. So I figured I'd go ahead and share my strategy.
Long before your baby should be capable of doing things (self-feeding, using a straw or a sippy cup, etc.), let them experiment! Self-feeding doesn't generally take place until the ninth month, sometimes even later, but Jude has been doing it since eight months, because I had been offering him bits of very soft food for two months by that point. During those months he mostly just picked the bits up and mashed them in his hand rather than get them anywhere near his mouth, but it was helping him with his pincer grip.
Babies generally don't start self-feeding with a utensil until after a year of age, but you bet your ass that Jude already owns his very own spoons! Though he doesn't use them to feed himself, he plays with them all the time. They are always available to him during the day. He can pick them up and practice manipulating them with his hands, sometimes he even pretends to feed himself.
I did the same thing with the sippy cup. We've given Jude small amounts of white grape juice since he was about six months old. Not to replace meals or quench his infant thirst, as breast milk is far superior in both regards, but because once he started solids he would get backed up once in a while and white grape juice is a natural, gentle stool softener. We'd give it to him in a bottle when he needed it, but when he didn't need it, I'd put a little in a sippy cup and leave it out for him. He could practice with is much as he would his spoon. To encourage him I'd take a few sips from it myself before setting it down.
Worked like a charm. He now drinks from it willingly between meals. Juice, milk, water, whatever is inside, he'll drink it from the sippy cup. In this way we've avoided him becoming reliant on the bottle, or the breast for that matter. He now uses all three interchangeably. Were I able to pump breast milk, I'd offer him that in the sippy cup too.
So my advice in summary, fellow parents, is don't go by the guidelines. Just because a book says they won't do it until ____, doesn't mean they can't do it earlier. Even if you don't expect your baby to hold his own spoon until eighteen months, give him one at five months. Let him chew on it and throw it around and make a big mess. So what if hes hows no interest in a sippy cup and refuses to drink out of anything but his bottle or the breast at six months, give him a sippy cup anyway. They're only disinterested until suddenly, it's the most interesting thing in the world. The transition later will be far less frustrating for everyone involved!
Disclaimer: Make sure the utensils you are giving for "play" are baby-safe. No metal or glass. Also be sure to supervise baby with these things, as with all things.