here is a bunch of links for you to look at, a few are video shorts
http://www.google.com/search?q=squar...=com.microsoft:en-US&ie=utf8&oe=utf8
it actually should of been squared up before you put the binding on. it was what i was taught.
i have used:
a
plumb line (chalk/with string, people use on walls to start wallpaper),also my husband has a T bar..aluminum thing they use to square and cut drywall.