To save the gurus the time of posting this tip I learned here....
Before removing the old belt, match-mark the side of the belt and the cam cogs and crank cog with white acrylic paint, paint pen or anything else that shows up well. When you remove the old belt line it up with the new belt (to determine they are the same size, same number of teeth) and then transfer the marks to the new belt. When you put the new belt on, line up the marks and be sure the marks are still lined up when the tensioner is snugged down.
Either before removing the old belt or after installing the new one, be sure the marks for the crank and cams actually line up with the marks on the engine... although I'd expect the engine operation to be pretty bad if it weren't right to start with.
Mike