Most schools require the FAFSA. For private schools, check if they also require the CSS Profile or their own supplemental form.
External transfer deadlines are often later than for incoming first-year student deadlines, but they vary widely. Check the specific deadlines for admissions and financial aid at each school.
Many other four-year institutions offer merit-based scholarships for transfer students. Research each school's policy.
Use a Net Price Calculator or view the Cost of Attendance on each school's website to get an early estimate of your out-of-pocket costs.