1) *** NOT RECOMMENDED*** Run both motors from the same motor driver, you can apparently get away with this if both motors combined do not exceed the capacity of the motor driver. But the driver will run hotter than the other axis, and will have less power which defeats the purpose in most cases.
2) Feed the pulse and direction signals from the same source. Easier to to with drivers that are separate and wired to a breakout board, though it could be done with a DB25 pass thru board that allowes pins to be jumpered together to do the same thing for all in one controller boards. There is a risk that whatever is driving your step and direction signals may not be able to drive two different drivers. Honestly, that is rarely an issue, but sometimes laptops with badly designed parallel ports can have issues if they are just being directly wired to the drivers, e.g. not through a BOB which provides buffering or isolation.
3) If your software supports it (Mach3 and LinuxCNC do), slave the motors together in axis configuration. You can find details of this by searching on 'slave axis' or 'slave motor' in the forum. This is the safest option. The only issue with that is not being able to have a 4th axis if you needed one for some reason.
Thanks to GrumpyGeek from CNCZone for most of this answer.