You would probably get more responses on the main
Theme Park Board
My main piece of advice has always been to avoid the Magic Kingdom on Saturdays.
Now withe Extra Magic Hours you can take one of two approaches:
1 - if you are staying onsite you can take advantage of the EMH and get there early and stay late
2 - avoid at all costs the EMH park and visit the park that had it the day before (example: if the MK has EMH on Monday, go to MK on Tuesday)...which has always been our approach - but we don't go in June.