Trust on the cookies of the website (worst option). Your selection will be stored in a cookie for your browser. The content of the cookie are your selected properties by activating the red heart at the property page.
The disadvantage of this option is that a cookie have a life time which expires or is rejected by your browser. In that case your favorites are not visible any more.
Register for a user account (best option). The most secure option for saving your selected properties is making a user account. As long as your account exists your selection will be stored and retrievable. A user account can easily be made by clicking the white/orange login button in the upper right corner next to the menu.