Do you love collecting airline miles? On your next hotel stay, you can accumulate enough miles for the trip of a lifetime or earn the 110,000 points required to qualify for the Southwest Companion Pass, which lets one person fly for free on Southwest with you for up to two years. There are plenty of ways you can net significant miles not just when staying at hotels, but also when you book a stay with Airbnb. Read on to get the scoop on how to leverage lucrative perks and points with these underrated hacks.[See: 7 Lesser-Known Ways to Use Your Loyalty Program Points or Miles.]Strategically Transfer Your Hotel Loyalty PointsMost hotel loyalty programs will let you convert your hotel points to airline miles. But there's a catch: Points often transfer at an unfavorable exchange rate, so it may not be the best value per point. For example, 10,000 Marriott Rewards points can be exchanged for 2,000 Southwest points, and 10,000 Hilton Honors points can be transferred for 1,500 American miles. Before you transfer your points, assess your spending habits and patterns to maximize value.Starwood Preferred Guest, on the other hand, offers a more favorable 1-to-1 transfer rate with a variety of airlines. Plus, Starwood Preferred Guest grants a bonus 5,000 miles for every 20,000 points a user converts. "Because of this awesome perk, I tend to use my Starwood American Express card for purchases where I wouldn't earn at least a 2x bonus [points] with another card," says Scott Lieberman, managing editor of rewards site MillionMileSecrets.com. "So I'm sure to bring my purple card to the dentist, auto mechanic and other such houses of pain. Then, I close my eyes and dream of my next vacation paid for with points," he adds.Use Booking Sites WiselyThere are a variety of third-party booking sites that allow you to earn airline miles when booking a hotel on their site. However, when you use these online travel agencies, you will forfeit any hotel loyalty points. Airlines like American and Southwest, on the other hand, offer booking sites that allow you to earn miles. On American Airlines and Southwest's sites, loyalty members can score up to 10,000 points per night on stays booked online. The miles appear in your account within a few days of checkout and can be a great way to pad your frequent flyer miles. Independent sites such as Rocketmiles.com and PointsHound.com also let users earn up to 10,000 miles per night and provide the flexibility of selecting from a variety of major frequent flyer programs, including the Alaska Airlines Mileage Plan and United MileagePlus.[See: 7 Smart Travel Credit Card Hacks You've Never Heard Of.]Invest in a Flexible Travel Credit CardUsing a credit card to pay for your stay is another way to stack miles. However, a flexible travel credit card that is not affiliated with a specific airline or hotel may be your best bet. "Do not use a hotel credit card if you're going to transfer the points to airlines miles, because that's almost always a bad deal," Lieberman says." Instead, get yourself a credit card that earns two, three or even five points per dollar on travel purchases," he says, explaining that travel purchases usually include hotels and Airbnb rentals, though it's a wise idea to check the fine print to confirm.Before choosing a flexible travel card, brush up on affiliated airline partners. "I often use my Chase Sapphire Preferred [Credit Card] to earn double points at hotels and Airbnb," Lieberman says. "So my $1,000 expense becomes 2,000 Chase Ultimate Rewards points. Then, I can transfer those 2,000 points to become 2,000 United miles, 2,000 Southwest miles or 2,000 British Airways miles and so on."To collect even more miles, use a card like the Chase Ink Business Cash Card that earns five points per dollar spent at office supply stores, where you can purchase Airbnb gift cards. Then, transfer the Chase points to various airlines and use the gift card to book your stay.Earn Delta SkyMiles With AirbnbWhile you can earn plenty of points with flexible travel credit cards on your Airbnb stays, there's also a direct way to earn additional miles. "Delta SkyMiles members can now earn 2 miles for every dollar spent on Airbnb rentals," says Roman Shteyn, CEO and co-founder of travel rewards site RewardExpert.com.[See: 50 Ways to Save More on Travel in 2018.]SkyMiles members can visit DeltaAirbnb.com to book their Airbnb through the site and earn double miles. Delta also frequently offers promotions where new members can both earn up to 5 miles per dollar spent and get a $25 credit on their first stay. What's more, if you sign up to become an Airbnb host through the site, you can earn up to 25,000 miles.50 Genius Money-Saving Travel Tricks Experts Know (That You Don't).