In addition to the already mentioned pheromone trails, ants are also very good at exactly retracing their steps.

Experiments testing this exact question found that if they added stilts to ant legs on their return trip found that they overshot their nest by the corresponding amount that their stride was lengthened by the stilts, implying that they are effectively counting steps as they retrace their path.

If these normal methods fail and they get lost, they’ll then enter a spiral search pattern until they find the nest or a trail.