you want a use year month that starts
before you typically travel. for booking june to august primarily, you would definitely want a
june use year (sept would be a terrible choice.)
UY month has
nothing to do with when you can call to book. nothing.
the 11 month booking window opens 11 months before travel at your home resort. the 7 month window works the same way - doesn't matter what UY month you have.
the issue with UY month is what happens if you need to cancel.
if you have a sept UY and book an august stay...and then find out in may that you need to cancel, you will find that you are up the creek since your banking window already closed at the end of april. your pts are all stuck in that use year and will expire at the end of august, whether you can find another way to use them or not.
if you have a june UY and book an august stay...and then find out in may that you need to cancel, you have until the end of the next january to bank any current year pts if you don't need to use them in that use year.
but whether you have a sept UY or a june UY, you can call in sept 2011 to book an aug 2012 stay (for a june contract - using current june 2012 pts, borrowed 2013 pts if needed and banked 2011 pts, if any). but if you never have to cancel, UY month is not a big issue...
more info on UY is here if you need it:
http://www.disboards.com/showthread.php?t=1942668