The phrase "word to the wise" is a warning that something important is about to be said. There are a number of synonyms for this phrase that can also convey this sense of caution or advice. For example, "heads up" is a short and snappy way of letting someone know that there is pertinent information they should be aware of. "Forewarned is forearmed" is another somewhat archaic phrase that means essentially the same thing, warning someone before they run into danger or a difficult situation. "Take heed" and "be advised" are other ways to convey a similar sense of urgency and importance. No matter which phrase one uses, the underlying message is clear: listen up, because this information could help you out in a big way.