[PyMOL] cartoons

[ALEX D. <ada...@ku...>]

dear all, 
i am new to pymol and i have a question about cartoons. 
i saw the demo of cartoon ribbons and really liked it, but i haven't
been able to get my protein displayed that way.  when i give the command
"cartoon automatic" all i get is a simple line that apparently traces
the backbone of my protein chain.  cartoon loop does the same thing. 
with "cartoon tube" i get a thicker line.  how do i set the parameters
so that i get nice helices and sheets like the ones showed in the demo?
thanks, 
alex