Masking objects in Illustrator CS 1

[kidanvil]

Whenever I mask some objects, I cant seem to get rid of all the excess. Its not visible until i click it. It shows that its blank, but its still there. Now normally i wouldnt mind, but when I export it for being printed on our wide format printer, it considers the invisible areas part of the print. this not only happens when mask, but drop shadows do the same thing. they extend over the white but visibly, it looks great. I hope i explained that ok. I just want whats visible to be what prints, or exports. even if i export the eps file with crop marks it doesnt work. thanks again, wish i found this forum a long time ago!