Passwords at home, I write down and file (with the exception of hyper-important stuff like bank access, where I choose passwords significant to to me and just write down clear hints that will help me get them but no-one else). I reckon that, if anyone gets access to those, I have bigger problems to worry about.
At work (softwear techie) I had, on average, 20-40 different password-protected access of various types. I (a) followed a theme meaningful to me (usually based on hobby things I'd been doing away from work); (b) used a single password on all systems; (c) guarded it carefully and changed it if I had the slightest suspicion it had been compromised; (d) changed it everywhere at the same time, regularly; (e) wrote down expired passwords so that I could recover any I accidentally failed to change; and (f) tried NEVR changed it immediately before going on leave. I found the combination of a password meaningful to me and the drill inherent in changing it multiple times in succession (and them using it regularly from that point on) meant that I never had a problem. Yes, I only had one password - one breach would have been a bigger exposure. But I NEVER had to write it down - and on the few occasions on which I had a brief memory glitch I could, in the worst case, give myself a big clue by looking back at my previous passwords to remind myself of my current "theme".