The tech that does your alignment must make sure that it is alignment with correct weight in the car (at the least a drivers weight) and a decent amount of fuel.
A steering wheel holder should also be used when adjusting front end alignment.
3 things that must be checked:
1) Thrust Angle must be 0.00.
2) Steering wheel must be centered and locked in center position.
3) Front and rear subframes must be centered and in true square position (usually a problem if there has been bushing work, or subframe work done. In rare cases, the subframe can shift, but again, rare.