Let's play it by ear
What it really means
Means "let's not fix a plan — we'll decide as we go". Between friends it is usually genuine flexibility. In response to an invitation, it can be a soft way to avoid committing.
Context, tips & common mistakes
Unlike its slippery cousins, "let's play it by ear" is usually sincere: it proposes genuinely deciding later, in response to how things unfold — which pub, whether to stay out, whether Sunday works. Among friends it is a relaxed, commitment-free yes-in-principle, and no one expects a plan until the day.
The skill is knowing when you need more than that. If you must book trains or tables, pin it down gently: "sounds good — shall we decide by Thursday?" converts vagueness into a deadline without breaching etiquette. And when a British friend answers your carefully structured itinerary with "let's just play it by ear", they are not rejecting you; spontaneity here is a form of comfort, not disrespect for your planning.