you can start by measuring from center to center of the wheel on left and right sides.
Also; the gaps in fender wells should be fairly close from wheel to wheel....this is NOT an exact measurement, but anything under 3/8" can be acceptable.
to do this:
A-go to LR tire and measure gap in front of tire to fender well, do the same at rear of that tire.
B-go to RR tire and do the same
C-compare measurements
Then measure rear toe IN/OUT (plenty of how-to's on you tube for this)
These are the free checks to do at home before frame or alignment shop/fees.