While you don't formally declare a major till during/after 3/c year, you should have some idea of what you want to do before scheduling 3/c classes. For example, this upcoming semester I'm in two EE-specific classes and an additional two math classes only technical majors take, which makes switching majors (particularly switching into an engineering major from government or management) virtually impossible after a certain point despite having not formally declared yet. You'll have plenty of time to figure out what you do and don't like during 4/c year as you'll be taking an engineering class (SED), a government-type class (history), etc.