Considering that many students enter college with an "undeclared" major or change their major one or more times once they begin college, this is a pretty common question. Your son is not alone. It is recommended to try and figure out the best field for him though before he starts. Some ways to do that:
- Have him think about what he enjoys doing outside of school. Do any of those interests or activities relate to specific fields?
- Take a personality and/or a career assesment test. MAPP (motivational appraisal or personal potential) is one example.
- Think about what classes he enjoyed, did well in, really thrived in. Are any of those areas he might major in?
- Through your network of friends and colleagues, have him talk with people in the careers that he thinks might be a fit.
- If through this he finds one or more that are of particular interest, research those, understand what the educational requirements are for that field. Definitely talk to someone doing it if possible.