Some people accept a referral for professional help more easily than others. It is usually best to be frank with a student about the limits of your ability to assist them - limits of time, energy, training, objectivity. It is often reassuring to a student to hear that you respect their willingness to talk to you and that you want to support them in getting the assistance that they need. Confused students may be comforted to know that they don't necessarily have to know what's wrong before they can ask for help.
Assure them that seeking help doesn't necessarily mean that they have serious problems. It is possible that their concern is one of the common reasons that college students seek the help of another person. These include feeling down or low on energy and motivation; experiencing difficulties in relationships with friends, parents, boy/girlfriends; feeling anxious or depressed; and having concerns about future goals or plans.
There are many kinds of referrals. The best one is the one the student will respond to. Depending on the situation, have the student consider friends, clergy, family members, community agencies, and campus offices, for example those in the Division of Student Affairs. If you can, try to prepare the student for what they might expect if they take your suggestion. Tell them what you know about the referral person or service.