How to make terminals open side-by-side?
This behavior won't happen in OS X by default, but a whole bunch of 3rd party window-arranging apps ought to be able to help:


SizeUp http://irradiatedsoftware.com/sizeup/
Divvy http://mizage.com/divvy/
Breeze http://www.autumnapps.com/breeze/
ShiftIt http://code.google.com/p/shiftit/
Mercury Mover http://www.heliumfoot.com/mercurymover/details
Optimal Layout http://most-advantageous.com/optimal-layout/
Cinch http://irradiatedsoftware.com/cinch/