In selecting colleges to which to apply, note that some appear to be more welcoming to transfer applicants than others. This site will help you compare transfer acceptance rates across a wide range of schools, as well as to first-year acceptance rates:

Transfer Admission Rates - College Transitions https://share.google/ZQlbA6iAPBEOziRZb

The transfer applicant, if applying to most selective schools, needs to be clear why he/she wants to transfer to the specific target school.

High school stats matter for those transferring after one semester or one year in college, but not sure about high school activities' relevance. Probably depends upon the particulars.

DS transferred after his sophomore year. The why essay question was very important. He expressed what he had already done that formed his current goals and how the transfer school would help him achieve those goals.

Compared to the endless advice about first year admission, there is very little on the web about how to approach a transfer app. Any helpful hints or tips — should essays focus only on college activities even if there was more leadership in high school; do you need to explain why current school not a fit or can you focus mostly on positives of transfer school? Anything to keep in mind?