WARNING: Do not over-torque the current trimpots. they will break. They have 270 degrees of travel only. 

Motor current for each axis is adjusted with the trimpot on the stepper driver.
Clockwise increases current, counter-clockwise decreases current. Some boards (EasyDriver) may be wired different so make sure you know how your stepperdivers are designed.

You want the motor current set slightly above the range you need for your application, but not much higher. Overdriving the motors draws more current and risks overheating or thermal shutdown.

Start by setting current to zero by gently turning the trimpot all the way down.
Then issue a very long Gcode command for that axis, something like g0x1000
Turn the trimpot up until the motor starts moving reliably.
You can hit the reset button and re-enter the Gcode command to verify that it will start at this current setting.
Note this lower bound pot setting.

Next continue to turn up the pot until the motor starts to cycle on and off - indicating thermal shutdown is occuring.
Now back off until the cycling stops.
Cycling will occur under thermal shutdown, and only gets more severe as the current goes up - where it appears the motor is stuttering.
Thermal shutdown is, of course, to be avoided, but we've never seen it actually damage the drivers or motors and we've seen some pretty abusive cases (actually, we caused them)!
Mark the spot just below thermal shutdown as the upper limit.
Now read about cooling to increase the upper limit.

Now is also a good time to make a mental note to enable Low Power Idle mode if you have a leadscrew-type machine or some other configuration that will hold position while idle without power being applied to the motors.