Here's an example

httrack -D -c3 -O "folder" <http://url.com/a/b/>

D *can only go down into subdirs (--can-go-down)
cN number of multiple connections (*c8) (--sockets[=N])

This is what I use most of the time,
varying only "folder" and url and -c
on dialup, I use no more than 3 sockets,
and on broadband no more than 6 (it's only fair)