The simple answer is you can't.
All the GPIO pins start as inputs see http://raspberrypi.stackexchange.com/a/38059/8697 and also http://raspberrypi.stackexchange.com/a/59216/8697
You need to design your interfacing circuitry properly (maybe less beeer), e.g. with appropriate pullups or pulldowns. NOTE the I²C pins have low onboard pullups.