Purchasing hotel room nights from Priceline or Hotwire without knowing the hotel name can be tricky. I’ve found a formula for getting hotel rooms for up to half off without ending up at a hotel you wouldn’t want to stay in.

Here’s what you need to know to get the best hotels possible from both sites, while still getting the mystery hotel discount.

1. Always look at reviews

I always look at the recommendation rating and the neighborhood before booking a hotel. If you have to take a cab because you booked too far away, you’re adding time and money to the price. I never book a hotel with less than a 70-80% recommendation rate on Hotwire. Priceline uses a scale of 1 to 10. I won’t book a hotel with a rating less than 7.

2. Priceline and Hotwire will tell you the last hotel that was booked under the deal

As soon as you click on a hotel, both Hotwire and Priceline will tell you the hotel the last person booked when choosing the mystery hotel option. Hotwire will also give you a sampling of four hotels it’s guaranteed to be. One trick to finding out what is likely the exact hotel is remembering that the mystery hotel will always say a percentage off the initial price you saved. If you look at the four hotels it could be that when purchased as a non-mystery hotel, you can add back the discount and see which hotel matches.

3. Know your nonnegotiable amenities

I book only pet-friendly hotels as I have a miniature schnauzer. Since these special deals are nonrefundable, it’s important you check the amenities list for any items that are absolutely necessary for you such as free breakfast, free parking or location. Also, remember that being pet-friendly doesn’t always mean there isn’t a charge. If you can figure out the hotel name first, call it quickly to check on its pet policy to make sure it doesn’t forbid your dog’s size.