Wow! I mostly disagree with the one that said no sippy cups, I have enough problems with spills and stained carpets to not have sippy cups. 18 month olds can't drink successfully from a regular cup, at least not right away, that takes a lot of time and patience and since you are working mom, you would be asking someone else to let your child spill and they have to take care of it... not cool. I have used a variety of sippy cups, the Nuby ones mentioned are good, but not necessarily the best. The rim isn't very wide, so the soft insert is easily pulled out by a child that bites on it (happened many times). My kids have all had sippy cups and none of them have stuck their tongues out as mentioned. If this worries you, Munchkin makes a sippy cup that has an edge on it so it feels like they are drinking from a real cup(http://www.munchkin.com/products/detail.html?section=prod.... Munchkin (and several others) make some really good training cups.
As for technique, I have one that has worked successfully for me and my family members (I did it first and told them about it, transition was a choice and made in less than a week). Fill the cup with your child's favorite drink, the one thing that they ask for the most, fill the bottle with a drink you are happy for them to choose, but that they don't usually want. For me it was sweet pediasure/milk mixture in the sippy cup (they thought they were getting chocolate or strawberry milk) and water in the bottle (both of my boys hated water but I would have been happy for them to have it). Then, when they were thirsty, I let them choose which drink they wanted. They could have the drink they really wanted, or the bottle, but not both. Within 4 days, I was able to put the bottles away forever and there was never a fight about it, it was their choice. You can always just make him switch over but I tried that with my older son and he was screaming. For him, giving him the choice was much better. My sister and sister-in-law both did this with their kids and it was 3 days for one and 6 days for the other... It works!