It is important to communicate your expectations clearly with your printer,
especially if you are doing work of any complexity. It helps if you can find
a shirt, either in the printers portfolio, or even elsewhere, that embodies
what you hope for, and discuss how it relates to what you expect. If such
concrete examples are not available then spend some time doing your best
to describe your standards. In most cases you should have some perception
of the expected results based on similar examples of the printers past work.
You should ask for samples to see what is possible.