Review other games. Not only review them, but take a time to leave a nice feedback to the developers. In most jams I took part, I could notice that when I left a feedback, the developer usually later also reviewed my game. And I gave priority to playing games from who gave me feedback. And that happens organically, no need to say in the end of the comment "please review my game too" ;)
More so, it is always nice to leave a positive feedback to other people.