The global hotel industry is expected to generate $550 billion in revenue in 2016, according to online statistics company Statista.com. The U.S. hotel industry represents a sizable percentage of that revenue: in 2014, it brought in $177 billion. The average daily rate for U.S. hotels during the same year was $113 – and that's expected to rise to $121 for 2015. Since 2011, the month with the highest average daily rate has been October, indicating that's a peak time to travel.

Accommodations represent a big chunk of any vacation budget, and what you pay depends on where you're going, the season and hotel availability. The good news: You may be able to save on hotel costs by following a few simple rules. Here they are.

Most hotel brands have revenue managers who forecast demand, search websites like Expedia.com to see what the competition is charging and analyze their own booking trends. Some hotels also look at overall travel trends, including airline ticket sales and the most popular days being searched on online booking sites. If airline ticket sales are up 15% in the market, for example, local hotels may bump up rates accordingly.

Weather also plays a role, especially for properties like beach and mountain resorts where people are planning on ideal conditions. If there's a particularly beautiful weather forecast, rates may rise in anticipation of increased demand. If bad weather's coming, there may be an increase in cancellations – and a drop in prices.

Because so many factors affect prices, it's difficult to pin down a one-size-fits-all best time to book (see The Best Times To Take A Vacation). A general rule of thumb, however, is to start checking prices for your destination at least 40 days in advance and keep monitoring the rates until you see a price you like. An easy way to keep an eye on rates is to sign up for a hotel price alert through one of the online travel aggregators, such as Kayak.com (see Online Travel Companies) Specify the city or hotel of your choice, the dates, the number of rooms/guests, how you want to receive the alerts (email or smartphones) – and how often you want to receive them, either daily or weekly.

Many hotels let you cancel up to a certain time on the day of your arrival (often 6 p.m.), without penalty. During peak travel times, holidays, or when there's a big event in town, however, the cancellation policy may be less forgiving . This is also true for many discounted rates, regardless of when and where you travel. It's a good idea to understand your hotel's cancellation policy – not just in the event you need to cancel your trip altogether, but in case you find a better hotel rate. Even if the hotel charges a fee for cancelling the reservation, it may still work out in your favor to cancel the first reservation, and then book the better deal. Do the math and make sure there's availability at the other hotel before cancelling your existing reservation.

It's possible to score great deals on hotels if you wait until the last minute. In general, you should reserve this option for shorter trips like weekend getaways or spontaneous get-togethers with your friends. It's not a good idea for longer trips or events you can't miss, like Grandma's 100^th birthday party. Last-minute booking websites are a good starting point – just search for last-minute booking hotel. These companies work with hotels to negotiate discounts on any unsold rooms (in many cases, hotels would rather have some money than no money). Some of the online travel aggregators also have sections dedicated to last-minute plans, such as TravelZoo.com's Last-Minute Travel Deals page where you can look up bargains by city.

In many cases, you'll get the best rate by contacting a hotel directly and asking about any specials, promotions and discounts they might have. To find the direct phone number, search for the hotel name plus the name of the city: for example, search for JW Marriott Orlando rather than JW Marriott. It's usually a number that starts with that city's area code, and not an 800 line.

Someone who works at that particular property – instead of the central reservation office – may be able to share rates that aren't advertised online or aren't available through the main office. Try calling a few times to ask about rates; you might end up with a rep who is more comfortable offering a better discount. And, it's worth mentioning, it pays to be nice and not demanding; remember, you're the one asking for a favor.

If they don't have any deals, ask about the corporate, American Automobile Association (AAA) or AARP rate, if any of these apply. And, if you're staying several nights or longer (and feeling lucky), you can ask if they'll offer a free night if you book X number of days. This probably won't work if you're staying during a peak time, but it's worth asking in case their numbers are down.

Lodging is a big part of any vacation budget, and just like searching for low airfares, it pays to know a few tricks. Since different factors go into the pricing models at each hotel – conventions, weather, airline ticket sales, recent TV promotions – prices can, and do, fluctuate in ways that aren't measurable across the hotel industry as a whole. As such, there is no magic time where you'll get the best rate on hotels everywhere. You'll have to do a little homework to get the best rates where and when you're traveling (see Websites That Save You Money On Hotel Rooms).

Start by checking prices at least 40 days in advance, and create alerts to notify you when prices change. Once you're comfortable with the rate, go ahead and book – especially if there's a good cancellation policy (you can cancel and book another reservation if you find a better deal). Booking last minute is an option for impromptu trips, but it's not worth the risk if you really have to be someone on a certain date. And don't forget to call the hotel directly: often, that's your best bet for getting good rates.