Normal paper won't work. Its too flimsy. You need something more
rigid, like a drawing block, for example. To make your model colour
last, and to make it more easy to clean, paste a sheet of plastic
over your printout. There is a kind of plastic which is sticky on
one side and you can cut it out to size. The plastic will also give
more strength to your paper model. However, be careful not to
create 'bubbles'. After that, cut out the various parts, fold and
paste them together. It takes lots of practice and patience to get
the lines to match accordingly. Failing which, your bus may be
lopsided or crooked.
I used to have several paper buses in my collection. Some people in
here have seen them. A few were crushed by my young cousins while
the rest eventually became encrusted with dust. I have no choice
but to 'retire' them. However, I still keep the templates in my PC.
Perhaps one day, I will find the time to build again.
Check this out.
http://www.angelfire.com/in/maranello/upgrade/pbm.html