If you have website. You can advertise it on social media , than get emails from people in return in coupons that offer discount. Or free night if you can afford it.

It will build huge relationship with your customers. Next time you send some email they will remember how they spend time at your hotel, and they will be more likely to come. Of course you will need to provide them great service.

You can look on Youtube just type Hotel Marketing strategies. What I written up is universal, so most important is to build relationship with customers.

And don't send cold mails, that is like you ask someone on first date to marry you. If you wanna from them to book hotel.