You can walk the Strip, but it is longer than it looks -- budget at least 30 minutes between major casinos. The Deuce is a bus service running up and down the Strip and beyond, 24/7. It is cheap but slow in traffic. The Las Vegas Monorail connects the Convention Center to the MGM Grand with stops in between, though it does not hit the most useful spots.
Taxis are the fastest option for short hops. Do not try to flag one down on the street -- it is illegal for drivers to pick up outside a cabstand. Only rent a car if you plan to leave Las Vegas proper; driving on the Strip during weekends is miserable.
Stay hydrated. The desert heat is deceptive -- you will not feel yourself sweating because it evaporates instantly. Drink plenty of water, especially if you are drinking alcohol. Wear comfortable shoes; the amount of walking catches everyone off guard.