I often tell people that the hardest way to earn airline miles is to step on an airplane. Even on the carriers that still offer you miles based on the distance you travel, you'll only earn about 500 miles per hour you spend on an airplane. And you'll have to spend an entire night in a hotel just to earn a few thousand points in their loyalty program.

In contrast, it takes just a few minutes to sign up for a credit card that can offer you 50,000 to 100,000 points or miles as a sign-up bonus. While 50,000 is competitive, the best offers will be in the 60,000 to 100,000 mile range.

With hotel points, a strong offer is one with enough points for at least two free nights in a mid-range hotel. But because hotel points are generally less valuable than airline miles, expect to receive 80,000 to 100,000 points from the best of these offers.

To receive these rewards, you'll typically have to meet a minimum spending requirement, often $3,000 to $5,000 within three months of account opening. However, some of the most generous offers will have even larger requirements. Also, most cards will have an annual fee, although some are waived the first year.

Once you've paid an annual fee and received your sign-up bonus, the last thing you'll want to do is cancel your card. Instead, try it out for a year and see how you like its rewards, benefits, and customer service. At the end of your fist year, you'll have all the information you need to decide if it's worth keeping or not.

10 Major Credit Card Bonuses for August 2018

Barclaycard Arrival Plus World Elite Mastercard

Welcome offer: New applicants can earn 60,000 bonus miles, worth $600 in travel statement credits, after spending $5,000 on new purchases within 90 days of account opening, and paying the annual fee.

Annual fee: $89

Comment: This card was briefly withdrawn from the market when Barclays introduced its Arrival Premier, with a $150 annual fee and no sign-up bonus. But now it's back with one of the most generous welcome offers seen on a card like this. This card offers double miles on all purchases, and you receive 5% of your redeemed miles back.

The Business Platinum Card from American Express

Welcome offer: Earn up to 100,000 Membership Rewards. Earn 50,000 points after you spend $10,000 and another 50,000 after spending an additional $15,000 on qualifying purchases within your first three months of account opening.

Annual fee: $450 (see rates and fees)

Comment: This is a large bonus, but it also has a very high minimum spending requirement. Still, this can be an attractive offer for small business owners looking to jump start their rewards balances. The annual fee is expensive, but it comes with enough perks, benefits, and travel fee reimbursements to justify it (see rates and fees).

Southwest Rapid Rewards Priority Credit Card

Welcome offer: Earn up to 60,000 points. You earn 40,000 points after you spend $1,000 on purchases within your account's first three months, and an additional 20,000 points after you spend a total of $12,000 on purchases within your account's first year.

Annual fee: $149

Comment: This premium card has just been introduced, with a great sign-up bonus. As with other Southwest cards, these bonus points should count towards the 110,000 you need to earn their Companion Pass. This card also offers you 7,500 bonus points each year after your cardmember anniversary, a $75 Southwest travel credit each year, and four upgraded boardings per year when available. Other features include 20% back on in-flight purchases, and 2x points per dollar spent on Southwest purchases and Rapid Rewards hotel and car rental partner purchases.

CitiBusiness / AAdvantage Platinum Select World Mastercard

Welcome offer: 70,000 bonus miles after spending $4,000 within the first four months of account opening.

Annual fee: $95, waived first year.

Comment: This card now offers double miles on purchases at telecommunications, car rental merchants, gas stations, and American Airlines purchases. You also receive a free checked bag, priority boarding, and discounts on in-flight food and beverages.

Platinum Delta SkyMiles Credit Card from American Express

Welcome offer: Earn 70,000 bonus miles and 10,000 Medallion Qualification Miles (MQMs) after you spend $3,000 in purchases on your new card within three months of account opening. This is a limited time offer available only until September 19, 2018.

Annual fee: $195

Comment: This is an attractive card that offers you a bunch of perks like free checked bags and priority boarding. But the biggest value here is the annual Companion Certificate that offers you a single domestic (contiguous 48 states) round-trip, economy class companion fare, plus government taxes and fees. This alone could be worth hundreds of dollars.

Southwest Rapid Rewards Premier Business Credit Card

Welcome offer: 60,000 points after spending $3,000 within the first three months of account opening.

Annual fee: $99

Comment: This is the best sign-up bonus ever seen for this card, and the points count towards the 110,000 necessary for their Companion Pass. It also features a 6,000-point bonus every year, on the cardholder's account anniversary.

The Platinum Card from American Express

Welcome offer: 60,000 Membership Rewards points after spending $5,000 within the first three months of account opening.

Annual fee: $550 (see rates and fees)

Comment: While the card's annual fee is among the highest, it also comes bundled with a $200 annual air travel fee statement credit, and a $200 annual Uber credit and a $100 credit towards the Global Entry or TSA PreCheck application. The card now offers a $50 credit towards Saks Fifth Avenue purchases twice a year. You also earn 5x points per $1 for flights booked through the airline and hotels booked with Amextravel.com (see rates and fees).

British Airways Visa Signature Card

Welcome offer: Up to 100,000 bonus Avios. 50,000 points after spending $3,000 within three months of account opening, an additional 25,000 bonus points after spending $10,000 total within your account's first year for a total of 75,000 bonus Avios. And another 25,000 bonus points after spending a total of $20,000 within your account's first year.

Annual fee: $95

Comment: There's a high minimum spending requirement to earn the total 100,000 points, but you can use these points for awards flights on Alaska, American, and other OneWorld partners.

Hilton Honors American Express Ascend Card

Welcome offer: Earn 100,000 Hilton Honors Bonus Points after you use your new card to make $2,000 in eligible purchases within the first three months of card membership.

Annual fee: $95

Comment: This card offers 12x points at participating Hilton portfolio hotels, 6x points at U.S. restaurants, U.S. supermarkets, and U.S. gas stations, and 3x points on all other purchases. You also receive Gold Elite status.

Starwood Preferred Guest Business Credit Card from American Express

Welcome offer: Earn 100,000 bonus points after spending $5,000 within three months of account opening. This limited offer is available until September 31, 2018.

Annual fee: $95, waived the first year (see rates and fees)

Comment: This card offers 6x points at over 6,500 participating SPG and Marriott Rewards properties. You also earn 4x points at U.S. restaurants, U.S. gas stations, wireless telephone services purchased directly from U.S. service providers, and on U.S. purchases for shipping, with 2x points for all other eligible purchases. You get a free night stay each year, Marriott Silver status, and Gold status when you spend $35,000 on purchases in a calendar year (see rates and fees).