So my big thing I would say is reading, commenting, and reccing. I read a lot in a verity of pairings over a plethora of fandoms. I really do my best to comment as much as possible, and I've been especially good about that in the HP fandom. And, of course, I keep track of my favorite for reccing purposes, but really so that I can go back and reread them when I'm in the mood. Basically I try and support all of the lovely people hwo create such wonderful things that I get to experience for free as much as I can
Last year, I also started modding, with two very different fests, which was fun. I started up and am a solo mod at hp_crossgenfest, a prompt-based fest focusing on any-Cross Gen pairing. Contrasted with hd_erised, a H/D exchange fest I started co-modding this year. I'm a very organized person and I really get a lot out of planning out all the little background details of modding, so it's been cool. And people seem to enjoy the fests, so yay contribution!
And, I just recently started writing. IDK that it's really much a "contribution to fandom" but I've been enjoying it. :D