Have fun! Don’t overwork yourself, be creative, take risks, and don’t forget to playtest! Remember that this is all just for fun and to improve. If you need tips on game jams, make sure to watch (or rewatch) Brackeys’ Video on it! 

Yeah, listen to this - there's a lot of "I'm ____ and this is my first game jam". I haven't exactly been doing game jams for a while, maybe only 4-5 months, but I have been making games since around 3 years ago. If you're going to listen to any advice you should pay attention to this, because it really is somewhat of a requirement to follow the above when doing game jams, some other 'game related' stuff has this apply to them in their own perspectives too.