coming back to Japanese after a break

I came back to studying Japanese after a several year hiatus, and I've been reading a lot and studying vocab with Memrise and Anki. For a while I had to study words I'm sure I used to know but just had trouble recognizing. It sounds like you were at a high level before, so I think reading would be a great way to get back into the language. You'll see where your weak points are and can determine what kind of study you might need from there. Reading/Listening to audiobooks with transcripts would be great as well--in fact that might be the fastest way to bring back your passive language skills.