Dual boot MacBook Air 2012 with Windows 7 - now boots directly into Windows
Shut down your MacBook, then hold down Option ⌥ key and turn it on. You will see a boot menu, choose OS X. When logged in into OS X, click System Preferences > Startup Disk, and choose which OS to start by default.

To set up Boot Camp drivers, download them via Boot Camp Assistant (WindowsSupport) folder, write the installers to a USB stick, and run from within Windows.