If you sign up with Visa Checkout through this link: Visa Checkout for Faster Hotel Booking | Marriott International (after logging in to your Marriott Rewards account), they will credit you with 500 bonus points. That's it! Nice and easy! Then, register your Marriott Rewards Visa Card (or any Visa card) and make a purchase through Visa Checkout (including at Marriott) within 15 days of activating your account and you will get another 500 bonus points! There is no minimum purchase amount mentioned, so you can refill your Starbucks card with $10 like I just did and you have satisfied the requirement and earned an additional 20 Marriott Rewards points (because all Starbucks purchases count as dining, even reloading your card online or through the app). You just have to select Visa Checkout as the payment method and login to your newly-created account. That's 1,020 points (or more) for doing essentially nothing.
If you already have Visa Checkout, you simply need to sign up with a different email address and a different Visa card than the one associated with your previous account (you will have to make sure the new email address matches the email address on your Marriott account - you can always change it back later). Then make sure that you log in to that new Visa Checkout account when checking out.
Oh, before you panic about not receiving your points, the terms and conditions specify that it may take up to 6-8 weeks after the promotion ends to receive your bonus points (of course).
You have until September 24, 2017 to sign up and 15 days thereafter to make your first purchase.