J.Forester How to Brake

My standard instruction for people who fear using the front brake
is the same instruction for teaching any person to brake properly.
Tell them to apply both brakes simultaneously, but with the front
brake 3 times harder than the rear brake. Start by accelerating to
road speed and stopping with a gentle application. Then do it again
with a harder application, but keeping the same 3 to 1 ratio. Then
again, harder still, until they feel the rear wheel start to skid.
When the rear wheel skids with 1/4 of the total braking force applied
to it, that shows that the weight distribution has now progressed as
far to the front wheel as the average cyclist should go. By repeated
practice they learn how hard this is, and attain confidence in their
ability to stop as rapidly as is reasonable without any significant
risk.
whole document
herehttp://www.faqs.org/faqs/bicycles-faq/part5/section-6.html