I think it's the case when the infinite form is required and there is no need for the verb conjugation. "Kак лучше дохать до магазина" If you compose the sentence: (not the best translation, but it's more understandable) - Better we will drive by the shortest way. "Лучше поедем коротким путем" in this case, you conjugate the verb. To conclude, conjugation depends on the sentence and context, but even there is only one verb in the sentence, it still can be in infinite form.