If you work 0.6, then you officially only have to attend 0.6 of staff meetings that are on a day you work. My school produces a timetable of what's being covered in staff meetings for this term, with asterisks next to the important ones they would like all staff to attend, so part-timers know. I work 0.8, and go to all meetings because I'm there, and as someone else says it builds goodwill.
I've had to negotiate various things with my Head this year though, and I'm lucky that she's fairly reasonable, and I am happy to stand my ground if I think it's necessary.
So for example there have been 2 INSETs on the day I don't work this year, one a report writing day, and one a 'class room environment' day - revamping working walls, displays, storage etc. Initially I was told not working those day was tough, I just wouldn't be given the time. But I then had a sensible conversation with my Head, asking her if my 0.2 job share was going to write all my reports and revamp my classroom on those days then, as he was in school on those days (0.2 job share is Deputy Head, who is very good but v busy and literally teaches the sessions on his day, marks the books and then is gone - he plans and teaches what I ask him to in the morning, does PE in the afternoon, and nothing more). Of course he wasn't going to do any of that, his INSET day was full of meetings and TA training etc, as they assume reports and classroom environment are my responsibility. And I just said that I it was unreasonable to expect me to do it all without the time all other class teachers were being given. So they paid me for the classroom day, and I came in, and they covered me with supply on one of my working days to so I could report write at home.