To consult means to seek advice, to refer to, to take into account, to consider, as one would consult an attorney or a physician. To consult also means to exchange views, to confer. As with service, consult has its roots in Latin: consultare, meaning to deliberate, counsel, consult or take counsel.
And consult means to advise, to recommend, to suggest, to provide an opinion about what could or should be done in a certain situation or in response to a certain problem. The consultant, therefore, is the expert applying her knowledge and expertise to improve the situation of a customer.
But essential to consulting a client is understanding his needs, his situation. This is done by first consulting with, meaning listening to that customer.
Advise: To give (someone) a recommendation about what should be done; to give information or notice to; to give a recommendation about what should be done; to talk with someone in order to decide what should be done.
Confer: To compare views or take counsel; to bestow from (or as if from) a position of superiority; to give as a property or characteristic to someone or something. From Latin conferre to bring together.
Counsel: Advice given especially as a result of consultation; a policy or plan of action or behavior. Middle English conseil, from Anglo-French cunseil, from Latin consilium, from consulere to consult.
Recommend: To present as worthy of acceptance or trial; to endorse as fit, worthy, or competent; to make acceptable. From Latin recommendare, from Latin re- + commendare to commend.
Suggest: To seek to influence; to call forth, evoke; to mention or imply as a possibility; to propose as desirable or fitting; to offer for consideration or as a hypothesis; to call to mind by thought or association; to serve as a motive or inspiration for. From Latin suggestus, past participle of suggerere to pile up, furnish, suggest, from sub- + gerere to carry.
Apply: To put to use especially for some practical purpose; to bring into action; to put into operation or effect; to employ diligently or with close attention; to have relevance or a valid connection; to make an appeal or request especially in the form of a written application. From Latin applicare, from ad- + plicare to fold.