If you like to travel, it's useful to sign in for reward programs. You can do it for airplane tickets, hotels, trains, ....
Up to a couple of years, we didn't do this. But now we are convinced it's a great thing. More than once now, I've been able to book Eurostar tickets with a reduction, or have one (even more) nights free in a hotel we like to stay at.
Sometimes, it allows you to travel practically free of charge. For instance, you can book a flight with miles you've saved up, and then have your hotel room with points... And then when this hotel is a Hilton and you pick an executive room, you only have to pay for lunch! (You get breakfast, snacks and happy hour for free.)
Also some bigger shops have such programs. Delhaize and Carrefour give points with every purchase you make. Once you have 500 points, you get a check for 5€ which you can exchange in the shop for special lines of presents, or it goes from the total you pay.
Just a few minutes ago, I've booked such a almost free stay in London later this year. Just like the previous year, ENO brings a muscial revival (last year it was Sunset Boulevard with Glen Close). They're bringing Caroussel with Katherine Jenkins and Alfie Boe. We were able to get tickets and now booked train and hotel.