Begin every activity with a task that 95 percent of the class can do without your help. Get your students used to the fact that when you say, "Please begin," they should pick up a pencil and start working successfully.
An interesting thought for my students who assume they can't do it and consistently sit and wait for teacher help; often without even looking at what they are supposed to do.
eachers tend to get the first response when they scaffold challenging tasks so that all students are successful.