How can a freshman who plans on transferring as a rising sophomore ensure that the letters of recommendation he receives stand out? That is, how can a professor write a strong LOR for a student whom he or she has only known for a semester? Does office hour attendance and strong performance in the class help out a lot in that regard?
Go above and beyond in assignments, talk to professor about subject during office hours and try to make small talk, keep them updated after you take the class, try to take the same professor if possible
Professors write these letters all the time. Get to know your professors, and be straight with them. Ask them what they need to see from you in order to write the best possible letter.