拋磚引玉

- throw away a brick in order to get a gem; (serve as) a modest spur to induce someone to come forward with his valuable contributions; break the ice; cast a brick to attract jade -- offer a few commonplace remarks by way of introduction so that others may come up with valuable opinions; cast away a brick and attract a jadestone; give a thing with a view of getting sth. better in return; throw [fling away] a sprat to catch a mackerel [a whale]; throw out a brick so as to draw pieces of jade; throw out a minnow to catch a whale