It depends.
A "last day to drop without academic penalty" is set by the University each semester; the date is available through the Registrar's website.
Prior to this deadline, students may drop a course through SOAR; the withdrawal appears as a "W" on official transcripts.
After this deadline, students can obtain a "drop" form from the department. Instructors are required to sign the form and assign a grade of "WP" [withdraw pass] or "WF" [withdraw fail].
Undergraduates can repeat courses a total of two times or a total of 6 semester hours in order to improve their grade point averages [only if the original grades were below a C*]. The grade for the second attempt will be used for computing grade point average.