I worked for a major motel chain as a Front Desk Clerk/Night Auditor and I learned some tricks of the trade about getting better rates then are listed. I’ve made reservations in Vegas, but never worked there so I can’t say for sure the same ‘tricks’ work at the better places. I stayed at the Stratosphere and it worked when I made reservations.
First, let me say that front desk clerks are given a range of rates with which to work from for each type of room.
Second, find out if there is a convention of any kind going to be in town the time you are going to be making reservations. Or any other special event… I’m thinking about Celine Dion opening her new act in Vegas is in March although I don’t remember when. The point here is if they don’t think they have to lower their prices to sell out, you don’t have much leverage.
There are also different kinds of discounts available for different types of groups, e.g. AAA discount, senior citizen discount, government employee, corporate rate, berevment, even internet discounts. Generally, these discounts range from 10-30% from the rack rate.
After you’ve done your homework … and by that I mean finding out what will be going on that weekend and calling the hotels you are interested in and asking them what their rates are … the basic rate, the AAA rate, the company rate (traveling on business)… And by all means, don’t identify yourself while doing your research. After you are armed with this information you are ready to go to work to negotiate the best rate possible.
When you call to make your reservation, before you ever give them your credit card, ask them “is that the best you can do?” when they quote you a rate. If they say, yes, that’s the best I can do, tell them that’s to high and counter with something about $5 lower then the lowest rate you’ve found during your research.
The person should counter with something lower then what they previously quoted (with a chuckle in their voice at your rediciously low rate). Keep after them. If they aren’t going to be very busy that weekend, you can usually expect to get a rate 20-25% lower then the rack rate. If they are going to be busy, you probably will be able to get the AAA/senior rate which is usually 10% lower. Although, some places won’t even recognize those discounts for big events.
Note: Be prepared to hang up if they won’t negotiate. Get the name of the person you are speaking with at the beginning of the conversation. Actually, get the name of the person you speak with when you call to get the various rates. Also, get their title. If you are working with a reservations agent or front desk clerk, you can always resort to asking for the assistant manager or manager. Don’t get on the phone when you don’t have time to spend negotiating. You and the other person should be tossing prices back and forth for a little while… Each time you going up a little and them coming down a little until you reach an amount you are comfortable with. Sometimes this happens quickly, but usually it takes awhile.
And, yes, even if you do hang up on one place, or 2 places, or all the places, you can always call the best one back but in order to get the best rate you were quoted during your conversation, you will need to be able to say something like “I spoke with Mary about 1 hour ago and she quoted me a rate of X. I’m ready to make my reservation now. Can I do that with you, or do I need to speak with Mary again?” ~~~ No, you shouldn’t have to speak with Mary again, but throwing out a name they recognize as being an employee there will make it very hard for the next person to say they can’t give you that low a rate.
And finally, when making your reservation, after you have finally given them your name and address but before you give them your credit card number, ask them THE question one more time… “Is that the best you can do”?
I don’t know if this site is any good or not, but I did run across it one day when I was surfing and bookmarked it so here it is: Las Vegas Talk Discussion Board
If something doesn’t make sense, drop me a note. My e-mail is in my profile.
FYI, there are tactics that work really well when walking in off the street while you are traveling and decide you need to stop, but they wouldn’t help you in this situation. Not totally different then these, just a little different… Just so you know the next time you are on the road. 
Good luck!