Midwest flights from MKE-LAS are on their "Saver Service" So the prices start out pretty low. Midwest does occasionally have coupon codes, but they are often limited to their traditional routes.

If price is your only consideration why not try priceline.com or hotwire.com?

If you have specific dates in mind, or you have to take a nonstop flight, why not consider a Midwest Airlines vacation package that included your hotel and plane tickets? Right now Midwest is running a promo that offers 10% off an entire Vegas package, I've attached some details from their newsletter below.

Some cool perks of booking a whole package include bonus miles, and passes to the Best Care Club in MKE

If you don't want a package, I would suggest booking your hotel rooms now (as long as you can cancel them with no penalty and thus keep looking for a better deal) and wait to book you plane tickets until about 2 months out

---------------------------

Save up to 10% by Booking Las Vegas Early

Las Vegas is great any time of year, but now you can save just by booking in advance. Stay at any of the MGM MIRAGE hotels this spring and enjoy great dining, exceptional shows and the best gaming in town. With 11 hotels and dozens of activities to choose from, let Midwest Airlines Vacation help you make the most of your next getaway.
Save up to 10% on all MGM MIRAGE air and hotel vacations.
Valid hotels include Bellagio, New York-New York Hotel and Casino, Luxor Las Vegas, The Mirage, MGM Grand Hotel and Casino, TI-Treasure Island, Circus Circus Hotel and Casino, THE Hotel at Mandalay Bay, Monte Carlo Resort and Casino, Mandalay Bay Resort and Casino, and Excalibur Hotel and Casino.
Book your vacation by December 31, 2005.
Travel January 1 through March 31, 2006.

http://www.midwestairlinesvacations....p?referrer=Y08
.