1. A method, implemented on at least one computing device each of which has at least one processor, storage, and a communication platform connected to a network for providing query suggestions, the method comprising the steps of: receiving a prefix of a query; identifying a plurality of query suggestions based on the prefix of the query, wherein the plurality of query suggestions include at least one entity; computing scores of each of the plurality of query suggestions using a first model, wherein the first model includes an adjustable parameter used for computing the score of the at least one entity; and ranking the plurality of question suggestions based, at least in part, on the scores.