I have a note book that i write all the series i have watched. It really comes in handy. In the middle i wrote the anime that i think are interesting but i know i'll forget the name or just anime i want to watch. Kinda like a 'Plan to watch" list in the middle.
On it i only write the series and the episode or season i'm on. at that certain anime. I mostly did this because i tend to start like 40+ series that i never get to finish and forget the episode i'm on :') sooo yeah
I also use My Anime List. I can keep track of the upcoming anime and also the anime i have on hold. I can also add there the certain movies and OVAs , seasons or idk. But it's a really good way