From the time airlines began introducing frequent-flier programs, business travelers realized they had a valuable opportunity. They could earn points on every business trip and put those points toward dream vacations. Over time, frequent-flier programs evolved and now travelers can get the same points through hotel chains and credit cards, opening up new opportunities to earn free flights and hotel stays.

Before you plan your next business trip, it's important to consider stocking up on rewards programs to avoid wasting an opportunity. Here are a few of the best frequent-traveler programs available to business travelers today.

If you've ever been a part of a frequent-flier program, you've likely experienced the numerous blackout dates that come up when you're trying to use your points. United Airlines MileagePlus program has earned criticism for this--but also has many fans. It will soon begin rewarding members for each dollar they spend on tickets rather than on the miles traveled. These points can be used for flights, hotels, shopping, and car rentals.

Marriott has found unique ways to let members use points, including rewards for social media shares and follows. Through a partnership with Hertz, members can save money and earn points through car rentals as well. Points can be converted into free nights in Marriott hotels and resorts, shopping sprees, and full travel packages. Members earn and use points at a variety of hotel properties, since the Marriott family of hotels includes the Ritz-Carlton, Courtyard, Springhill Suites, Fairfield Inn & Suites, Residence Inn, and TownePlace Suite.

Emerald Club members get VIP treatment with their car rentals, including access to all rental vehicles for discounted prices. Emerald Club membership also allows the traveler to skip the counter and get an e-receipt when the car is returned, saving time and paper. If you buy 12 paid rentals or 40 paid rental days in a year, you'll get executive status, which gives you a choice of full-size rental cars and automatic upgrade to the next car class up.

With Starwood Preferred Guest, you'll receive points for every hotel stay with no blackout dates during redemption. The company lets users choose between nine hotel brands, including Aloft, Weston, and Sheraton. Your points can be redeemed for hotel or resort stays, premium concert tickets, and backstage passes.

To save money and time, many businesses now use discount travel sites to book hotels, air travel, and car rentals. Expedia's rewards program gives members two points for each dollar of travel booked through its site, which can be used to book hotels or flights for yourself or someone else. Members also have access to perks like spa discounts and free drinks at select +VIP Access hotels.

If you want to keep things simple and earn points for every travel dollar you spend on your business, consider a credit card that earns rewards toward trips. While there are many credit cards that offer rewards, Chase Sapphire Preferred is often recommended for high points-to-spend ratio. Spend $3,000 in your first three months and you'll earn 40,000 points, which adds up to $500 toward airfare or rewards if you book travel through its Ultimate Rewards program. For each dollar spent in a restaurant or on travel, you'll earn two points, plus you'll get 20 percent off all of the travel you redeem through Ultimate Rewards. However, after the first year, you'll pay $95 each year and the interest rate is 15.99 percent. While you won't have the benefit of Chase's travel club, you may find a better deal on a rewards card through your bank.

Travel rewards programs are a great way for professionals to save money on fun-filled vacations by doing nothing more than signing up. These rewards programs are among the best, but almost every hotel chain, car rental service, and airline has frequent traveler programs, so you can likely earn rewards using the services you prefer to use. With these plans, you'll enjoy each business trip more, knowing you're working toward a great vacation.