Debugging /bin/sh scripts?

[Krzys Majewski]

What's a good way to debug /bin/sh scripts? I thought there
was an interpreter option which would run the code line by
line, prompting after each line, but I looked through the
man/info pages and found nothing, or am I blind? I already
know about sh -x and sh -v, but these by themselves are still
a bit rough to use. If I get a good tip here I may never have
to write C code again ;) 
-chris