You read the install guide and FAQ?
Did you check the Windows on Mac Boot Camp forum?
www.apple.com/support/bootcamp has how to etc
You installed the Apple Windows Support Software
You have looked in Windows Control Panels : Boot Camp : Change default startup
There is also Startup Disk in System Preferences in OS X
x = Mac OS X
Option key invokes Mac boot OS selector on startup
MacBook ProMac 101: Using Windows on your Mac via Boot Camp
Helpful Apple Support Resources (Forum Overview)
Boot Camp 4.0, OS X Lion: Frequently asked questionhttp://support.apple.com/kb/HT4818
create a Windows support software (drivers) CD or USB storage media
The Boot Camp Assistant can burn Boot Camp software (drivers) to a DVD or copy it to a USB storage device, such as a flash drive or hard drive. These are the only media you can use to install Boot Camp software.
Instructions for all features and settings.