As you may know drinks are free in Las Vegas as long as you're dropping money into a machine or playing at one of the table games. You can, however, score free drinks if you're watching someone else play or if you're just standing around in the Casino. The trick is to tip well. It sounds simple but if you're sitting at the 25 cent slots tip the waitress $2 dollars and I will guarantee you she will be back by the time your next drink needs to be ordered. What I typically do is tip the waitress $5 right off the bat just so that she understands I'm not a cheap ass. This goes a long way. After the initial tip $1 is all that's needed. If you're winning drop a few more dollars in. If you're playing at a one of the tables the chances are good you will see more waitresses come by but just to be sure pop in a good tip and you will easily have your fill of adult beverages.
Of all the things that change in Las Vegas drinks are still cheap if you gamble. Hit the nightclubs and you'll be amazed just how much they can charge you for alcohol.