I eyeball the tire, with emphasis on the front, against the ST and DT. I'll look at the chainstays too but they don't necessarily indicate wheel alighment w.r.t. the front half of the frame unless they were brazed into positions exactly symmetric on the BB. (Presumably the stays would be symmetric on a good bike, but you never know.)

However either improper wheel dish or asymmetric rear DOs would make that visual position wrong. Wheel dish could have been done poorly by whoever built or "adjusted" the wheel, and a previous owner (or the factory) resetting the rear spacing poorly could have gotten the DOs asymmetric. However the vertical position of the DOs is harder to screw up, or is at least more likely to be unaffected by a previous owner. So for a quick test the wheel dish can be judged against the brake mounting bolt. If the wheel is known to be true w.r.t. the brake bolt even if the DOs are themselves asymmetric, then the front of the wheel can be aligned to the ST.