If you wish to avoid making mistakes which are either costly or time-wasting, the 3 main things to avoid in Vegas are:
1 gambling while drunk; it’s the easiest way to lose money, since gambling (slots or tables) requires lucid, strong will power to stop before you lose more than you can afford. With regards to playing slot machines (and this is something most people fall victims to) you must avoid being ‘hypnotized’ by the machine; to many people fail to get up and change machine (or exit the casino) when it’s clear that the only way is down. We talk about this in detail on how to win in Vegas casinos.
2wandering away on foot from the main tourist areas, especially at night. It’s quite easy to take a wrong turn and end up in a dodgy area. This can happen everywhere but especially North Strip and in downtown Vegas.
3 uncomfortable shoes; by all means bring your fancy outfits if you plan to go to a high-end restaurant or club, but comfortable shoes are probably the most important item you will need to bring. No matter what you plan, you will need to walk significant distances (even just within your resort) and ‘tourist Vegas’ is filled with people walking barefoot because their feet are sore.
4 Checking into rooms which overlook or are near the pool (if you don’t like loud noise).
Some resorts, especially during weekends, pump up music very loud from early morning (as in the case of Excalibur); this means that you won’t be able to sleep from 8am.
More on this on What you Need to Know in Vegas.